U.S. patent number 7,356,399 [Application Number 10/543,313] was granted by the patent office on 2008-04-08 for failure determination system for stepless speed changer and failure determination device for start clutch.
This patent grant is currently assigned to Honda Motor Co., Ltd.. Invention is credited to Takahiro Eguchi, Takahiro Matsuda, Ukyo Ogata.
United States Patent |
7,356,399 |
Eguchi , et al. |
April 8, 2008 |
Failure determination system for stepless speed changer and failure
determination device for start clutch
Abstract
There is provided a failure determination system for a
continuously variable transmission of a belt type, which is capable
of determining failure of control valves for performing speed
varying operation, and enhancing maintainability. An ECU controls a
transmission ratio of the transmission to a fixation-determining
LOW-side range when the vehicle is standing. When the transmission
ratio during stoppage of the vehicle is within a stop-time OD-side
range if engine torque.gtoreq.OD-time DR-side reference torque and
at the same time the transmission ratio<DN-side reference value
hold, the ECU determines that the DR solenoid valve is faulty, and
if the throttle valve opening.gtoreq.OD-side reference value, the
transmission ratio.gtoreq.DN-side reference value, and at the same
time a vehicle speed<OD-side reference value hold, the ECU
determines that the DN solenoid valve is faulty.
Inventors: |
Eguchi; Takahiro (Saitama-ken,
JP), Ogata; Ukyo (Saitama-ken, JP),
Matsuda; Takahiro (Saitama-ken, JP) |
Assignee: |
Honda Motor Co., Ltd. (Tokyo,
JP)
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Family
ID: |
32828905 |
Appl.
No.: |
10/543,313 |
Filed: |
January 28, 2004 |
PCT
Filed: |
January 28, 2004 |
PCT No.: |
PCT/JP2004/000744 |
371(c)(1),(2),(4) Date: |
March 16, 2006 |
PCT
Pub. No.: |
WO2004/068003 |
PCT
Pub. Date: |
August 12, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060169036 A1 |
Aug 3, 2006 |
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Foreign Application Priority Data
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Jan 29, 2003 [JP] |
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2003-021221 |
Jan 29, 2003 [JP] |
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2003-021222 |
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Current U.S.
Class: |
701/61; 192/103F;
192/48.601; 192/48.609; 477/46; 477/48; 477/50; 73/1.01;
73/168 |
Current CPC
Class: |
F16D
48/066 (20130101); F16H 61/12 (20130101); F16D
2500/1026 (20130101); F16D 2500/3067 (20130101); F16D
2500/3108 (20130101); F16D 2500/3144 (20130101); F16D
2500/5108 (20130101); F16H 61/662 (20130101); F16H
2061/1208 (20130101); F16H 2061/126 (20130101); Y10T
477/6243 (20150115); Y10T 477/6242 (20150115); Y10T
477/62427 (20150115) |
Current International
Class: |
G06F
7/00 (20060101); G06F 17/00 (20060101); G06F
19/00 (20060101) |
Field of
Search: |
;701/61 ;73/168,1.01
;477/46,48,50 ;192/85R,103F |
References Cited
[Referenced By]
U.S. Patent Documents
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1153914 |
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63031835 |
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Feb 1988 |
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63074736 |
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Apr 1988 |
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02201021 |
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05118420 |
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3461329 |
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JP |
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vol. 3 Digital Object I. cited by examiner.
|
Primary Examiner: Nguyen; Cuong
Attorney, Agent or Firm: Arent Fox LLP
Claims
What is claimed is:
1. A failure determination system for a continuously variable
transmission including a drive pulley which has torque input from a
drive source of a vehicle, and whose pulley width is reduced by
supply of oil pressure, a driven pulley which is connected to the
drive pulley via a belt, and whose pulley width is reduced by
supply of oil pressure, and a drive-side control valve and a
driven-side control valve that control the oil pressure supplied
from a hydraulic system to the drive pulley and the driven pulley,
respectively, so as to carry out speed varying operation, the
failure determination system determining failure of any of the
drive-side control valve and the driven-side control valve, the
failure determination system comprising: transmission
ratio-detecting means for detecting a transmission ratio between
the drive pulley and the driven pulley; vehicle speed-detecting
means for detecting a vehicle speed of the vehicle; and
failure-determining means for determining failure of at least one
of the drive-side control valve and the driven-side control valve,
based on the transmission ratio detected at one of a time during
stoppage of the vehicle and a time immediately before the stoppage
of the vehicle, the transmission ratio detected after a restart of
the vehicle after the stoppage, and the detected vehicle speed.
2. A failure determination system as claimed in claim 1, wherein
the transmission ratio at one of the time during stoppage of the
vehicle and the time immediately before the stoppage of the vehicle
is set to a value within a predetermined low-speed range, and
wherein when the transmission ratio detected at the one of the time
during stoppage of the vehicle and the time immediately before the
stoppage of the vehicle is within the predetermined low-speed
range, and at the same time the vehicle speed is increased to a
predetermined vehicle speed or higher after the restart of the
vehicle after the stoppage, unless the transmission ratio is
reduced to a value lower than the predetermined low-speed range,
said failure-determining means determines that there has occurred
at least one of a failure in which the drive-side control valve is
fixed in a state where the drive-side control valve has stopped the
supply of oil pressure to the drive pulley, and a failure in which
the driven-side control valve is fixed in a state where the
driven-side control valve continues the supply of oil pressure to
the driven pulley.
3. A failure determination system as claimed in claim 1, wherein
the transmission ratio at one of the time during stoppage of the
vehicle and the time immediately before the stoppage of the vehicle
is set to a value within a predetermined low-speed range, and
wherein when the transmission ratio detected at one of the time
during stoppage of the vehicle and the time immediately before the
stoppage of the vehicle is within a predetermined high-speed range
lower than the predetermined low-speed range, said
failure-determining means determines that there has occurred at
least one of a failure in which the drive-side control valve is
fixed in a state where the drive-side control valve continues the
supply of oil pressure to the drive pulley, and a failure in which
the driven-side control valve is fixed in a state where the
driven-side control valve has stopped the supply of oil pressure to
the driven pulley.
4. A failure determination system as claimed in claim 3, further
comprising start operation-detecting means for detecting start
operation of the vehicle, wherein when the transmission ratio
detected at one of the time during stoppage of the vehicle and the
time immediately before the stoppage of the vehicle is within the
predetermined high-speed range lower than the predetermined
low-speed range, and at the same time the start operation of the
vehicle is detected, if the transmission ratio is increased to a
value equal to or higher than a predetermined low-speed
transmission ratio higher than the predetermined high-speed range,
and at the same time the vehicle speed is lower than a second
predetermined vehicle speed, said failure-determining means
determines that there has occurred the failure in which the
driven-side control valve is fixed in the state where the
driven-side control valve has stopped the supply of oil pressure to
the driven pulley.
5. A failure determination system for a continuously variable
transmission including a drive pulley which has torque input from a
drive source of a vehicle, and whose pulley width is reduced by
supply of oil pressure, a driven pulley which is connected to the
drive pulley via a belt, and whose pulley width is reduced by
supply of oil pressure, and a drive-side control valve and a
driven-side control valve that control the oil pressure supplied
from a hydraulic system to the drive pulley and the driven pulley,
respectively, so as to carry out speed varying operation, the
failure determination system determining failure of any of the
drive-side control valve and the driven-side control valve, wherein
a transmission ratio between the drive pulley and the driven pulley
at one of a time during stoppage of the vehicle and a time
immediately before the stoppage of the vehicle is set to a value
within a predetermined low-speed range, the failure determination
system comprising: transmission ratio-detecting means for detecting
the transmission ratio; torque-detecting means for detecting torque
input to the drive pulley; and failure-determining means for
determining that there has occurred a failure in which the
drive-side control valve is fixed in a state where the drive-side
control valve continues the supply of oil pressure to the drive
pulley, on condition that the transmission ratio at the one of the
time during stoppage of the vehicle and the time immediately before
the stoppage of the vehicle is within a predetermined high-speed
range lower than the predetermined low-speed range, that the torque
detected by said torque-detecting means after a restart of the
vehicle after the stoppage is larger than a predetermined torque,
and that the transmission ratio is not increased to a predetermined
low-speed transmission ratio higher than the predetermined
high-speed range, after the restart of the vehicle after the
stoppage thereof.
6. A failure determination system for a hydraulically-controlled
start clutch that is disposed between a transmission to which
torque is input from a power source of a vehicle and drive wheels
of the vehicle, for being engaged by supply of oil pressure thereto
from a hydraulic system via a control valve, such that an engaging
force of the start clutch is controlled according to an input
command to the control valve, the failure determination system
determining failure of the control valve, the failure determination
system comprising: vehicle start operation-detecting means for
detecting a start operation of the vehicle; vehicle speed-detecting
means for detecting a vehicle speed of the vehicle; rotational
speed parameter-detecting means for detecting a rotational speed
parameter indicative of a rotational speed of the power source; and
failure-determining means for determining failure of the control
valve based on a result of detection by said vehicle start
operation-detecting means, the input command to the control valve,
the detected vehicle speed, and the detected rotational speed
parameter.
7. A failure determination system as claimed in claim 6, wherein
said failure-determining means determines that the control valve is
faulty, on condition that the vehicle starting operation has been
detected, that a value of the input command to the control valve is
within a predetermined range, that the detected vehicle speed is
lower than a predetermined vehicle speed, and that the rotational
speed parameter indicates that the rotational speed of the power
source is equal to or higher than a predetermined value.
8. A failure determination system for a hydraulically-controlled
start clutch that is installed on a vehicle, the start clutch being
disposed between a continuously variable transmission of a belt
type including a drive pulley which has torque input from a drive
source of the vehicle, a driven pulley, and a belt stretched around
the drive pulley and the driven pulley, and drive wheels of the
vehicle, for being engaged by supply of oil pressure thereto from a
hydraulic system via a control valve, such that an engaging force
of the start clutch is controlled according to an input command to
the control valve, the failure determination system determining
failure of the control valve, the failure determination system
comprising: vehicle start operation-detecting means for detecting a
start operation of the vehicle; vehicle speed-detecting means for
detecting a vehicle speed of the vehicle; rotational speed
parameter-detecting means for detecting a rotational speed
parameter indicative of a rotational speed of the power source; and
failure-determining means for determining failure of the control
valve based on a result of detection by said vehicle start
operation-detecting means, the input command to the control valve,
the detected vehicle speed, and the detected rotational speed
parameter.
9. A failure determination system as claimed in claim 8, wherein
said failure-determining means determines that the control valve is
faulty, on condition that the vehicle starting operation has been
detected, that a value of the input command to the control valve is
within a predetermined range, that the detected vehicle speed is
lower than a predetermined vehicle speed, and that the rotational
speed parameter indicates that the rotational speed of the power
source is equal to or higher than a predetermined value.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application is a National Stage entry of International
Application No. PCT/JP2004/000744 filed Jan. 28, 2004, the entire
specification claims and drawings of which are incorporated
herewith by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a failure determination system for a
continuously variable transmission of a belt type which has a belt
stretched between two pulleys of a variable pulley width type, and
performs speed varying operation by varying the pulley widths of
the pulleys by oil pressure supplied thereto via control valves,
and a failure determination system for a start clutch disposed
between a transmission and drive wheels of a vehicle and having the
engaging force thereof controlled by oil pressure supplied thereto
via a control valve, and more particularly to determination of
failure of these control valves.
2. Description of the Related Art
Conventionally, a failure determination system for a continuously
variable transmission has been disclosed e.g. in Japanese Laid-Open
Patent Publication (Kokai) No. S60-157553 (pages 2-12 and FIG. 13).
The continuously variable transmission is installed on a vehicle,
and comprised of a drive pulley of a variable pulley width type to
which torque from an engine is input, a driven pulley of a variable
pulley width type connected to the drive pulley via a belt, a
hydraulic circuit including three solenoid valves for controlling
oil pressure supplied to the drive pulley and the driven pulley,
and a controller connected to the three solenoid valves via three
electric drive circuits. In the continuously variable transmission,
command signals from the controller are input to the solenoid
valves via the electric drive circuits, respectively, to control
the solenoid valves, thereby supplying oil pressure from the
hydraulic circuit to the drive pulley and the driven pulley to
change the pulley widths of the pulleys, whereby the speed varying
operation of the continuously variable transmission is carried
out.
Further, the failure determination system includes two rotational
speed sensors for detecting the respective rotational speeds of the
drive pulley and the driven pulley. In the failure determination
system, the inputs and outputs of the electric drive circuits are
compared with each other during travel of the vehicle, whereby it
is determined whether or not a disconnection or a short circuit has
occurred in the solenoids of two of the solenoid valves for
supplying oil pressure to the drive pulley (step SR13 in FIG. 13 of
the publication). Further, during travel of the vehicle, the actual
transmission ratio of the continuously variable transmission is
calculated based on signals delivered from the two rotational speed
sensors, and determination of whether the speed varying operation
of the continuously variable transmission is faulty is executed
based on the difference between the detected actual transmission
ratio and a target transmission ratio (steps SR16 to SR19 in FIG.
13 of the publication).
According to the conventional failure determination system, the
determination of whether or not a disconnection or a short circuit
has occurred in the solenoids of the solenoid valves is performed
separately from the determination of faulty speed varying operation
of the continuously variable transmission, and hence it is possible
to discriminate failure of the solenoids and failure of the
hydraulic circuit of the continuously variable transmission from
each other. However, each solenoid valve is comprised of a
combination of a solenoid and hydraulic circuit components, such as
a valve element, not only the solenoid but also the hydraulic
circuit-components can become faulty. For example, there are cases
in which the valve element is fixed in the open-state or the
closed-state, e.g. due to a foreign matter contained in oil.
Further, in the hydraulic circuit of the continuously variable
transmission, a foreign matter in oil or a small amount of oil
leakage at a location other than the three solenoid valves can
cause shortage of oil pressure supplied to the pulleys. However, in
the above failure determination system, only the failure
determination of the solenoids of the solenoid valves is carried
out, so that it is impossible to discriminate failure of a
hydraulic circuit component of the solenoid valves from failure of
components of the hydraulic circuit other than the solenoid valves.
As a result, even when only a hydraulic circuit component of the
solenoid valves is faulty, the faulty component cannot be
identified, but it is only possible to determine the failure of the
hydraulic circuit as a whole. To locate a faulty portion of the
hydraulic circuit, it is necessary to check the entire hydraulic
circuit, which results in degraded maintainability of the
continuously variable transmission. Particularly when locating of a
faulty portion is impossible, it is necessary to replace the whole
hydraulic circuit.
A determination system for a start clutch arrange in the drive
system of a vehicle has been conventionally proposed e.g. in
Japanese Laid-Open Patent Publication (Kokai) No. H02-176265 (pages
4-5 and FIG. 6). This failure determination system is for
determining failure of a lockup clutch of a torque converter, and
comprised of an engine speed sensor for detecting an engine speed,
a TM rotational speed sensor for detecting a TM rotational speed
input to a transmission, and a microcomputer to which all of these
sensors are connected. Further, a solenoid valve is connected to
the microcomputer, for controlling oil pressure supplied via a
hydraulic circuit to the lockup clutch according to a command
signal from the microcomputer, whereby the engaging force of the
lockup clutch is controlled.
In the proposed failure determination system, when the command
signal is input to the solenoid valve from the microcomputer,
thereby controlling the lockup clutch to the engaged state, failure
of a lockup system including the solenoid valve and the hydraulic
circuit is determined based on results of comparison between the
engine speed and the TM rotational speed, in other words, based on
the results of comparison between the input-side rotational speed
of the lockup clutch and the output-side rotational speed of the
same. More specifically, when a slip ratio as a quotient of
division of the difference between the engine speed and the TM
rotational speed by the engine speed is more than a predetermined
value B (3%), it is determined that the lockup system is faulty.
Further, in this failure determination system, the command signal
input to the solenoid of the solenoid valve is compared with a
monitor signal monitoring the solenoid from a monitor circuit of a
drive circuit, whereby occurrence of a disconnection or a short
circuit in the solenoid is determined.
Further, a start clutch arrange between an automatic transmission
of the drive system of a vehicle and drive wheels of the same has
been conventionally proposed e.g. in Japanese Laid-Open Patent
Publication (Kokai) No. 2002-39352 (pages 4-5 and FIG. 1). In this
start clutch, an electric control valve controls oil pressure
supplied from an oil pressure pump to the start clutch whereby the
engaging force of the start clutch is controlled. Further, the
automatic transmission is implemented by a continuously variable
transmission of a belt type having a belt stretched around two
variable pulleys.
When the conventional failure determination system disclosed in
Japanese Laid-Open Patent Publication (Kokai) No. H02-176265 is
applied to the start clutch disclosed in Japanese Laid-Open Patent
Publication (Kokai) No. 2002-39352, there arises the following
problems: According to the conventional failure determination
system disclosed in Japanese Laid-Open Patent Publication (Kokai)
No. H02-176265, the determination of whether or not a disconnection
or a short circuit has occurred in the solenoid of the solenoid
valve is performed separately from the determination of failure of
the lockup system, and hence it is possible to discriminate failure
of the solenoid and failure of the lockup system from each other.
However, according to this failure determination system, only the
failure determination of the solenoids is carried out, so that it
is impossible to discriminate failure of a hydraulic circuit
component of the solenoid valves from failure of components of the
hydraulic circuit other than the solenoid valves, for the same
reason described hereinabove as to the conventional failure
determination system for a continuously variable transmission. As a
result, even when only a hydraulic circuit component of the
solenoid valve is faulty, the faulty component cannot be
identified, but it is only possible to determine the failure of the
hydraulic circuit as a whole. To locate a faulty portion of the
hydraulic circuit, it is necessary to check the entire hydraulic
circuit, which results in degraded maintainability of the start
clutch. Particularly when locating of a faulty portion is
impossible, it is necessary to replace the whole hydraulic
circuit.
SUMMARY OF THE INVENTION
It is a first object of the present invention to provide a failure
determination system for a continuously variable transmission of a
belt type, which is capable of determining failure of control
valves for performing speed varying operation, and enhancing
maintainability of the transmission.
It is a second object of the present invention to provide a failure
determination system for a start clutch, which is capable of
determining failure of a control valve for controlling the engaging
force of the start clutch, and enhancing maintainability of the
start clutch.
To attain the first object, in a first aspect of the present
invention, there is provided a failure determination system for a
continuously variable transmission including a drive pulley which
has torque input from a drive source of a vehicle, and whose pulley
width is reduced by supply of oil pressure, a driven pulley which
is connected to the drive pulley via a belt, and whose pulley width
is reduced by supply of oil pressure, and a drive-side control
valve and a driven-side control valve that control the oil pressure
supplied from a hydraulic system to the drive pulley and the driven
pulley, respectively, so as to carry out speed varying operation,
the failure determination system determining failure of any of the
drive-side control valve and the driven-side control valve,
the failure determination system comprising:
transmission ratio-detecting means for detecting a transmission
ratio between the drive pulley and the driven pulley;
vehicle speed-detecting means for detecting a vehicle speed of the
vehicle; and
failure-determining means for determining failure of at least one
of the drive-side control valve and the driven-side control valve,
based on the transmission ratio detected at one of a time during
stoppage of the vehicle and a time immediately before the stoppage
of the vehicle, the transmission ratio detected after a restart of
the vehicle after the stoppage, and the detected vehicle speed.
With the arrangement of the failure determination system according
to the first aspect of the invention, determination of failure of
at least one of the drive-side control valve and the driven-side
control valve is carried out based on transmission ratios detected
during stoppage of the vehicle and after a restart of the vehicle
after the stoppage, and a detected vehicle speed, so that it is
possible to accurately determine the failure of the drive-side
control valve and the driven-side control valve, by discriminating
the failure from a failure caused by shortage of oil pressure from
the hydraulic system. For example, when the transmission ratio
indicates a low-speed side value in spite of a high vehicle speed,
it can be determined, irrespective of the shortage or sufficiency
of oil pressure supplied from the hydraulic system, that oil
pressure is not supplied to the drive pulley owing to the failure
of the drive-side control valve, whereby the width of the drive
pulley is controlled to a wide width for a low-speed transmission
ratio, and/or that the oil pressure is excessively supplied to the
driven pulley owing to the failure of the driven-side control
valve, whereby the width of the driven pulley is controlled to a
narrow width for the low-speed transmission ratio. Inversely, when
the transmission ratio indicates a high-speed side value in spite
of a low vehicle speed, it can be determined, irrespective of the
shortage or sufficiency of oil pressure supplied from the hydraulic
system, that oil pressure is excessively supplied to the drive
pulley owing to the failure of the drive-side control valve,
whereby the width of the drive pulley is controlled to a narrow
width for the high-speed transmission ratio, and/or that oil
pressure is not supplied to the driven pulley owing to the failure
of the driven-side control valve, whereby the width of the driven
pulley is controlled to a wide width for the high-speed
transmission ratio. As described above, it can be determined that
the failure of at least one of the drive-side control valve and the
driven-side control valve.
Preferably, the transmission ratio at one of the time during
stoppage of the vehicle and the time immediately before the
stoppage of the vehicle is set to a value within a predetermined
low-speed range, and when the transmission ratio detected at the
one of the time during stoppage of the vehicle and the time
immediately before the stoppage of the vehicle is within the
predetermined low-speed range, and at the same time the vehicle
speed is increased to a predetermined vehicle speed or higher after
the restart of the vehicle after the stoppage, unless the
transmission ratio is reduced to a value lower than the
predetermined low-speed range, said failure-determining means
determines that there has occurred at least one of a failure in
which the drive-side control valve is fixed in a state where the
drive-side control valve has stopped the supply of oil pressure to
the drive pulley, and a failure in which the driven-side control
valve is fixed in a state where the driven-side control valve
continues the supply of oil pressure to the driven pulley.
With the arrangement of this preferred embodiment, the transmission
ratio at one of the time during stoppage of the vehicle and the
time immediately before the stoppage of the vehicle is set to a
value within a predetermined low-speed range, and hence when the
transmission ratio detected at one of the time during stoppage of
the vehicle and the time immediately before the stoppage of the
vehicle is within the predetermined low-speed range, it is presumed
that the width of the drive pulley is controlled to the wide width
for the low-speed transmission ratio, and at the same time the
width of the driven pulley is controlled to the narrow width for
the low-speed transmission ratio, and hence that the two control
valves normally operate. However, when the vehicle speed is
increased to a value equal to or higher than a predetermined
vehicle speed after the restart of the vehicle after the stoppage,
unless the transmission ratio is reduced to a value lower than the
predetermined low-speed range, i.e. unless the transmission ratio
is changed to a high-speed transmission ratio, it can be determined
that there has occurred a failure in which the drive-side control
valve is fixed in a state where the drive-side control valve has
stopped the supply of oil pressure to the drive pulley, whereby the
oil pressure is not supplied to the drive pulley to cause the width
of the drive pulley to be controlled to the wide width for the
low-speed transmission ratio, and/or that there has occurred a
failure in which the driven-side control valve is fixed in a state
where the driven-side control valve continues the supply of oil
pressure to the driven pulley, whereby the oil pressure is
excessively supplied to the driven pulley to cause the width of the
driven pulley to be controlled to the narrow width for the
low-speed transmission ratio. As described above, since it is
possible to specifically determine the failure of at least one of
the drive-side control valve and the driven-side control valve, the
continuously variable transmission can be repaired more easily than
the prior art simply by replacing at least one of the two control
valves, thereby making it possible to enhance maintainability of
the continuously variable transmission.
Preferably, the transmission ratio at one of the time during
stoppage of the vehicle and the time immediately before the
stoppage of the vehicle is set to a value within a predetermined
low-speed range, and when the transmission ratio detected at one of
the time during stoppage of the vehicle and the time immediately
before the stoppage of the vehicle is within a predetermined
high-speed range lower than the predetermined low-speed range, the
failure-determining means determines that there has occurred at
least one of a failure in which the drive-side control valve is
fixed in a state where the drive-side control valve continues the
supply of oil pressure to the drive pulley, and a failure in which
the driven-side control valve is fixed in a state where the
driven-side control valve has stopped the supply of oil pressure to
the driven pulley.
With the arrangement of this preferred embodiment, the transmission
ratio at one of the time during stoppage of the vehicle and the
time immediately before the stoppage of the vehicle is set to a
value within a predetermined low-speed range, and hence, when the
transmission ratio detected at one of the time during stoppage of
the vehicle and the time immediately before the stoppage of the
vehicle is within a predetermined high-speed range lower than the
predetermined low-speed range, it can be determined that there has
occurred a failure in which the drive-side control valve is fixed
in a state where the drive-side control valve continues the supply
of oil pressure to the drive pulley, whereby the oil pressure is
excessively supplied to the drive pulley to cause the width of the
drive pulley to be controlled to the narrow width for the
high-speed transmission ratio, and/or that there has occurred a
failure in which the driven-side control valve is fixed in a state
where the driven-side control valve has stopped the supply of oil
pressure to the driven pulley, whereby the oil pressure is not
supplied to the driven pulley to cause the width of the driven
pulley to be controlled to the wide width for the high-speed
transmission ratio. As described above, since it is possible to
specifically determine the failure of at least one of the
drive-side control valve and the driven-side control valve, the
continuously variable transmission can be repaired more easily than
the prior art simply by replacing at least one of the two control
valves, thereby making it possible to enhance maintainability of
the continuously variable transmission.
Preferably, the failure determination system further comprises
start operation-detecting means for detecting start operation of
the vehicle, and when the transmission ratio detected at one of the
time during stoppage of the vehicle and the time immediately before
the stoppage of the vehicle is within the predetermined high-speed
range lower than the predetermined low-speed range, and at the same
time the start operation of the vehicle is detected, if the
transmission ratio is increased to a value equal to or higher than
a predetermined low-speed transmission ratio higher than the
predetermined high-speed range, and at the same time the vehicle
speed is lower than a second predetermined vehicle speed, the
failure-determining means determines that there has occurred the
failure in which the driven-side control valve is fixed in the
state where the driven-side control valve has stopped the supply of
oil pressure to the driven pulley.
With the arrangement of this preferred embodiment, when the
transmission ratio detected at one of the time during stoppage of
the vehicle and the time immediately before the stoppage of the
vehicle is within the predetermined high-speed range lower than the
value within the predetermined low-speed range, it can be
determined that at least one of the drive-side control valve and
the driven-side control valve is faulty, as described above.
Further, in the case of the start operation of the vehicle being
detected, even if the drive pulley is driven to the narrow width
for the high-speed transmission ratio owing to the failure of the
drive-side control valve, so long as the driven-side control valve
is normal, there cannot be caused a state where the transmission
ratio is increased to a value equal to or higher than the
predetermined low-speed transmission ratio higher than the
predetermined high-speed range in spite of the vehicle speed being
lower than the second predetermined vehicle speed. Therefore, when
the above state occurs, it can be determined that a significant
slippage is occurring between the driven pulley and the belt by the
failure in which the driven-side control valve is fixed in the
state where the driven-side control valve has stopped the supply of
oil pressure to the driven pulley. This makes it possible to
accurately identify the failure of the driven-side control valve.
As described above, since it is possible to identify the failure of
the driven-side control valve, it is possible to more easily repair
the continuously variable transmission simply by replacing the
driven-side control valve, thereby making it possible to further
enhance maintainability of the continuously variable
transmission.
To attain the first object, in a second aspect of the present
invention, there is provided a failure determination system for a
continuously variable transmission including a drive pulley which
has torque input from a drive source of a vehicle, and whose pulley
width is reduced by supply of oil pressure, a driven pulley which
is connected to the drive pulley via a belt, and whose pulley width
is reduced by supply of oil pressure, and a drive-side control
valve and a driven-side control valve that control the oil pressure
supplied from a hydraulic system to the drive pulley and the driven
pulley, respectively, so as to carry out speed varying operation,
the failure determination system determining failure of any of the
drive-side control valve and the driven-side control valve,
wherein a transmission ratio between the drive pulley and the
driven pulley at one of a time during stoppage of the vehicle and a
time immediately before the stoppage of the vehicle is set to a
value within a predetermined low-speed range,
the failure determination system comprising:
transmission ratio-detecting means for detecting the transmission
ratio;
torque-detecting means for detecting torque input to the drive
pulley; and
failure-determining means for determining that there has occurred a
failure in which the drive-side control valve is fixed in a state
where the drive-side control valve continues the supply of oil
pressure to the drive pulley, on condition that the transmission
ratio at the one of the time during stoppage of the vehicle and the
time immediately before the stoppage of the vehicle is within a
predetermined high-speed range lower than the predetermined
low-speed range, that the torque detected by the torque-detecting
means after a restart of the vehicle after the stoppage is larger
than a predetermined torque, and that the transmission ratio is not
increased to a predetermined low-speed transmission ratio higher
than the predetermined high-speed range, after the restart of the
vehicle after the stoppage thereof.
With the arrangement of the failure determination system according
to the second aspect of the invention, when the transmission ratio
at one of the time during stoppage of the vehicle and the time
immediately before the stoppage of the vehicle is within a
predetermined high-speed range lower than the predetermined
low-speed side, it can be determined that at least one of the
drive-side control valve and the driven-side control valve is a
faulty state as described above. Further, after the vehicle is
restarted after the stoppage, when torque detected by the
torque-detecting means is larger than a predetermined torque, and
at the same time the transmission ratio is not increased to a
predetermined low-speed transmission ratio higher than the
predetermined high-speed range, it can be determined that no
significant slippage is occurring between the drive pulley and the
belt, or between the driven pulley and the belt, in spite of large
torque input to the drive pulley. Even when the driven pulley is
actuated to the wide width for the high-speed transmission ratio
owing to the failure of the driven-side control valve, the above
state cannot be caused so long as the driven-side control valve is
normal, since the transmission ratio is changed to a low-speed
value. Therefore, when the above state occurs, it can be determined
that there has occurred the failure in which the drive-side control
valve is fixed in the state where the drive-side control valve
continues the supply of oil pressure to the drive pulley, whereby
the drive pulley is controlled to the narrow width for the
high-speed transmission ratio. This makes it possible to accurately
identify the failure of the drive-side control valve. As described
above, since it is possible to identify the failure of the
drive-side control valve, it is possible to easily repair the
continuously variable transmission simply by replacing the
drive-side control valve, thereby making it possible to enhance
maintainability of the continuously variable transmission. (It
should be noted that throughout the specification, the term
"detection of torque" includes not only direct detection of torque
by a sensor but also calculation of the torque).
To attain the second object, in a third aspect of the present
invention, there is provided a failure determination system for a
hydraulically-controlled start clutch that is disposed between a
transmission to which torque is input from a power source of a
vehicle and drive wheels of the vehicle, for being engaged by
supply of oil pressure thereto from a hydraulic system via a
control valve, such that an engaging force of the start clutch is
controlled according to an input command to the control valve, the
failure determination system determining failure of the control
valve,
the failure determination system comprising:
vehicle start operation-detecting means for detecting a start
operation of the vehicle;
vehicle speed-detecting means for detecting a vehicle speed of the
vehicle;
rotational speed parameter-detecting means for detecting a
rotational speed parameter indicative of a rotational speed of the
power source; and
failure-determining means for determining failure of the control
valve based on a result of detection by the vehicle start
operation-detecting means, the input command to the control valve,
the detected vehicle speed, and the detected rotational speed
parameter.
With the arrangement of the failure determination system according
to the third aspect of the invention, the engaging force of the
start clutch is controlled according to the input command to the
control valve. This allows determination of failure of the control
valve based on a result of detection by the vehicle start
operation-detecting means, the input command to the control valve,
the detected vehicle speed, and the detected rotational speed
parameter. For example, in a state where the vehicle starting
operation is detected, even if the supply of oil pressure from the
hydraulic system is short, in spite of supply of oil pressure which
is high enough to generate the sufficiently strong engaging force
of the start clutch, if the vehicle speed does not rise, it can be
determined that owing to the failure of the control valve, the oil
pressure is not supplied to the start clutch, so that the engaging
force is so small that the power from the transmission is not
transferred to the drive wheels, or that the vehicle is climbing a
hill. In such a state, if the rotational speed parameter indicates
a rise in the rotational speed of the power source, it can be
determined that the vehicle is not climbing a hill, but the control
valve is faulty. Thus, the failure of the control valve can be
identified, which makes it possible to repair the start clutch
simply by replacing the faulty control valve, and thereby improve
maintainability of the start clutch.
Preferably, the failure-determining means determines that the
control valve is faulty, on condition that the vehicle starting
operation has been detected, that a value of the input command to
the control valve is within a predetermined range, that the
detected vehicle speed is lower than a predetermined vehicle speed,
and that the rotational speed parameter indicates that the
rotational speed of the power source is equal to or higher than a
predetermined value.
With the arrangement of the preferred embodiment, as described
above, the engaging force of the start clutch is controlled
according to the input command to the control valve, by setting the
predetermined range to such a range that even if the supply of oil
pressure from the hydraulic system is short, it is expected that
due to the input command, the start clutch is supplied with an oil
pressure high enough to generate an engaging force of the start
clutch strong enough to cause the vehicle to start, if the vehicle
starting operation is detected, and at the same time, the command
input to the control valve is within the predetermined range, it
can be presumed that the start clutch should be sufficiently
engaged, and the vehicle should make a standing start and shift to
a traveling condition. In spite of such conditions, if the vehicle
speed is lower than the predetermined vehicle speed, it can be
determined that the oil pressure is not supplied to the start
clutch owing to the failure of the control valve irrespective of
shortage of supply of oil pressure from the hydraulic system, so
that the engaging force of the start clutch is not strong enough to
transfer the power from the transmission to the drive wheels, or
that the vehicle is climbing a hill. In such a case, if the
rotational speed parameter indicates that the rotational speed of
the power source is equal to or higher than a predetermined value,
it can be determined that the vehicle is not climbing a hill, but
that owing to the failure of the solenoid valve, the power is not
transferred from the transmission to the drive wheels. In short,
the failure of the control valve can be accurately identified.
To attain the second object, in a fourth aspect of the present
invention, there is provided a failure determination system for a
hydraulically-controlled start clutch that is installed on a
vehicle, the start clutch being disposed between a continuously
variable transmission of a belt type including a drive pulley which
has torque input from a drive source of the vehicle, a driven
pulley, and a belt stretched around the drive pulley and the driven
pulley, and drive wheels of the vehicle, for being engaged by
supply of oil pressure thereto from a hydraulic system via a
control valve, such that an engaging force of the start clutch is
controlled according to an input command to the control valve, the
failure determination system determining failure of the control
valve,
the failure determination system comprising:
vehicle start operation-detecting means for detecting a start
operation of the vehicle;
vehicle speed-detecting means for detecting a vehicle speed of the
vehicle;
rotational speed parameter-detecting means for detecting a
rotational speed parameter indicative of a rotational speed of the
power source; and
failure-determining means for determining failure of the control
valve based on a result of detection by the vehicle start
operation-detecting means, the input command to the control valve,
the detected vehicle speed, and the detected rotational speed
parameter.
With the arrangement of the failure determination system according
to the fourth aspect of the invention, the determination of failure
of the control valve is carried out based on a result of detection
by the vehicle start operation-detecting means, the input command
to the control valve, the detected vehicle speed, and the detected
rotational speed parameter. Therefore, as described above, while
discriminating from the case of the vehicle climbing a hill, it can
be determined that the failure of the control valve, irrespective
of shortage of the oil pressure supplied from the hydraulic system.
Thus, differently from the prior art, it is possible to identify
the failure of the control valve, which makes it possible to repair
the start clutch simply by replacing the control valve, thereby
improve maintainability of the same.
Preferably, the failure-determining means determines that the
control valve is faulty, on condition that the vehicle starting
operation has been detected, that a value of the input command to
the control valve is within a predetermined range, that the
detected vehicle speed is lower than a predetermined vehicle speed,
and that the rotational speed parameter indicates that the
rotational speed of the power source is equal to or higher than a
predetermined value.
With the arrangement of the preferred embodiment, as described
above, the engaging force of the start clutch is controlled
according to the input command to the control valve, by setting the
predetermined range to such a range that even if the supply of oil
pressure from the hydraulic system is short, it is expected that
due to the input command, the start clutch is supplied with an oil
pressure high enough to generate an engaging force of the start
clutch strong enough to cause the vehicle to start, if the vehicle
starting operation is detected, and at the same time the command
input to the control valve is within the predetermined range, it
can be presumed that the start clutch should be sufficiently
engaged, and the vehicle should make a standing start and shift to
a traveling condition. In spite of such conditions, if the vehicle
speed is lower than the predetermined vehicle speed, it can be
determined that the oil pressure is not supplied to the start
clutch owing to the failure of the control valve irrespective of
shortage of supply of oil pressure from the hydraulic system, so
that the engaging force of the start clutch is not strong enough to
transfer the power from the transmission to the drive wheels, or
that the vehicle is climbing a hill. In such a case, if the
rotational speed parameter indicates that the rotational speed of
the power source is equal to or higher than a predetermined value,
it can be determined that the vehicle is not climbing a hill, but
that owing to the failure of the solenoid valve, the power is not
transferred from the transmission to the drive wheels. In short,
the failure of the control valve can be accurately identified.
The above and other objects, features, and advantages of the
present invention will become more apparent from the following
detailed description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a skeleton diagram schematically showing the arrangement
of a drive system of a vehicle including a continuously variable
transmission and a start clutch to which a failure determination
system according to an embodiment of the present invention is
applied;
FIG. 2 is a block diagram schematically showing the arrangement of
the failure determination system and a hydraulic circuit of the
drive system;
FIG. 3A is a diagram schematically showing a state where the pulley
width of a drive pulley is controlled to a wide width for a
low-speed transmission ratio;
FIG. 3B is a diagram schematically showing a state where the pulley
width of the drive pulley is controlled to a narrow width for a
high-speed transmission ratio;
FIG. 4A is a diagram schematically showing a state where the pulley
width of a driven pulley is controlled to a narrow width for the
low-speed transmission ratio;
FIG. 4B is a diagram schematically showing a state where the pulley
width of the driven pulley is controlled to a wide width for the
high-speed transmission ratio;
FIG. 5 is a flowchart showing a main routine for carrying out a
solenoid valve monitoring process;
FIG. 6 is a flowchart showing a subroutine carried out for an
executable condition determining process;
FIG. 7 is a flowchart showing a subroutine carried out for a travel
incapability determining process;
FIG. 8 is a diagram showing an example of a TH-NERUNG table for use
in calculation of a first travel incapability reference value
NERUNNG;
FIG. 9 is a diagram showing an example of a TH-NERUNG table for use
in calculation of a second travel incapability reference value
NERUNNG;
FIG. 10 is a flowchart showing a subroutine carried out for a
fixation determining process for determining fixation of an SC
solenoid valve;
FIG. 11 is a diagram showing an example of a NE-THSCFOK table for
use in calculation of an SC normality reference value THSCOFOK;
FIG. 12 is a timing chart showing an example of operations executed
in a case (indicated by curves of broken lines) in which the SC
solenoid valve is normal, and a case (indicated by curves of solid
lines) in which the SC solenoid valve is fixed in the fully-closed
state;
FIG. 13 is a flowchart showing a subroutine carried out for a
fixation determining process for determining fixation of a DR
solenoid valve and a DN solenoid valve;
FIG. 14 is a flowchart showing a subroutine carried out for a
stop-time transmission ratio determining process;
FIG. 15 is a flowchart showing a subroutine carried out for an
OD-side determining process;
FIG. 16 is a continuation of the FIG. 15 flowchart;
FIG. 17 is a diagram showing an example of a TH-RATIO-TQDRJD map
for use in calculation of OD-time DR-side reference torque
TQDRJD;
FIG. 18 is a flowchart showing a subroutine carried out for a
LOW-side determining process;
FIG. 19 is a timing chart showing an example of operations executed
in a case where at least one of fixation of the DR solenoid valve
in the fully-closed state and fixation of the DN solenoid valve in
the fully-open state has occurred when a transmission ratio RATIO
during stoppage of the vehicle is within a stop-time LOW-side
range;
FIG. 20 is a timing chart showing an example of operations executed
in a case where at least one of fixation of the DR solenoid valve
in the fully-open state and fixation of the DN solenoid valve in
the fully-closed state has occurred when the transmission ratio
RATIO during stoppage of the vehicle is within a stop-time OD-side
range;
FIG. 21 is a timing chart showing an example of operations executed
in a case where only the fixation of the DR solenoid valve in the
fully-open state has occurred when the transmission ratio RATIO
during stoppage of the vehicle is within the stop-time OD-side
range; and
FIG. 22 is a timing chart showing an example of operations executed
in a case where only the fixation of the DN solenoid valve in the
fully-closed state has occurred when the transmission ratio RATIO
during stoppage of the vehicle is within the stop-time OD-side
range.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention will now be described in detail with reference to
drawings showing a preferred embodiment thereof. Referring first to
FIG. 1, there is schematically shown the arrangement of a drive
system of an automotive vehicle 3 including a continuously variable
transmission 20 and a start clutch 30 to which a failure
determination system 1 according to the present embodiment is
applied. FIG. 2 schematically shows the arrangement of the failure
determination system 1 and a hydraulic circuit 28 of the drive
system. The failure determination system 1 is comprised of an ECU
2, referred to hereinafter, and various sensors 40 to 47, referred
to hereinafter, and the ECU 2 carry out various types of failure
determination on solenoid valves, as described in detail
hereinafter.
As shown in FIG. 1, in the drive system of the vehicle 3, an engine
4 as a drive source is connected to drive wheels 7 and 7 via a
forward/backward travel-switching mechanism 10, a continuously
variable transmission of a belt type 20, the start clutch 30, and a
differential gear mechanism 6, whereby the torque of the engine 4
is transferred to the drive wheels 7 and 7.
The forward/backward travel-switching mechanism 10 includes an
input shaft 11, and a planetary gear mechanism 12 mounted on the
input shaft 11. The input shaft 11 has one end connected to a
crankshaft 4a of the engine 4 via a flywheel 5, and rotatably
extends through a hollow main shaft 21. The planetary gear
mechanism 12 is comprised of a sun gear 12a, a carrier 12d for
rotatably supporting a plurality of (e.g. four) pinion gears 12b
mating with the sun gear 12a, and a ring gear 12c mating with the
pinion gears 12b.
The sun gear 12a is integrally formed with the input shaft 11, and
the input shaft 11 has a portion thereof on the engine side with
respect to the sun gear 12a, connected to an inner plate 13a of a
forward clutch 13. Further, an outer plate 13b of the forward
clutch 13 is connected to the ring gear 12c and the main shaft 21.
The engagement and disengagement of the forward clutch 13 is
controlled by the ECU 2. The carrier 12d has a reverse brake 14
connected thereto. The operation of the reverse brake 14 is also
controlled by the ECU 2.
Due to the construction described above, in the forward/backward
travel-switching mechanism 10, when the vehicle 3 is moved forward,
the reverse brake 14 is released, and the forward clutch 13 is
engaged, whereby the input shaft 11 and the main shaft 21 are
directly connected to each other to directly transmit the rotation
of the input shaft 11 to the main shaft 21, while the pinion gears
12b do not rotate about their axes, and the carrier 12d idly rotate
in unison with the input shaft 11 in the same direction. Thus,
during the forward movement of the vehicle 3, the main shaft 21
rotate in the same direction as the input shaft 11 at the same
rotational speed.
On the other hand, when the vehicle 3 is moved backward, inversely
to the above, the forward clutch 13 is disengaged but the reverse
brake 14 is locked to thereby lock the carrier 12d to inhibit
rotation thereof. This causes the rotation of the input shaft 11 to
be transmitted to the ring gear 12c via the sun gear 12a and the
pinion gears 12b, whereby the ring gear 12c and the main shaft 21
connected thereto rotate in a direction opposite to the direction
of rotation of the input shaft 11. Thus, during the backward
movement of the vehicle 3, the main shaft 21 rotates in the
direction opposite to the direction of rotation of the input shaft
11.
The continuously variable transmission 20 is a so-called belt-type
CVT, and comprised of the main shaft 21, a drive pulley 22, a
driven pulley 23, a counter shaft 25, a drive pulley width variable
mechanism 26, and a driven pulley width variable mechanism 27.
The drive pulley 22 has a moving part 22a having a truncated
conical shape, and a fixed part 22b. The moving part 22a is mounted
to the main shaft 21 such that it is axially movable but
unrotatable thereabout, while the fixed part 22b is disposed in a
manner opposed to the moving part 22a, and fixed to the main shaft
21. Further, opposed surfaces of the moving part 22a and the fixed
part 22b are formed to provide inclined surfaces, whereby a
V-shaped belt groove for causing the belt 24 to extent therein is
formed between the moving part 22a and the fixed part 22b.
The drive pulley width variable mechanism 26 is for changing the
pulley width of the drive pulley 22, and includes a DR oil chamber
26a formed within the moving part 22a, a DR solenoid valve 26b for
controlling the oil pressure supplied to the DR oil chamber 26a,
and a return spring (not shown) for urging the moving part 22a
toward the fixed part 22b.
As shown in FIG. 2, the DR solenoid valve 26b is disposed between
an oil pressure pump 28a of the hydraulic circuit 28 (hydraulic
system) and the DR oil chamber 26a in the moving part 22a, and
connected to them via respective oil passages 28b and 28b. The oil
pressure pump 28a (hydraulic system) is connected, though not
shown, to the crankshaft 4a of the engine 4, for being driven by
the crankshaft 4a during the operation of the engine 4, to thereby
deliver the oil pressure. This causes the oil pressure delivered
from the oil pressure pump 28a to be constantly supplied to the DR
solenoid valve 26b via the oil passage 28b.
The DR solenoid valve 26b is of a normally-open type comprised of a
combination of a solenoid and a spool valve (neither of which is
shown), and electrically connected to the ECU 2. When no input
command DRCMD (electric signal) is supplied from the ECU 2, the DR
solenoid valve 26b is held in the fully-open state, that is, at the
maximum valve opening, to thereby supply oil pressure from the oil
pressure pump 28a to the DR oil chamber 26a via the oil passages
28b. Further, the DR solenoid valve 26b is configured as a linear
solenoid valve whole valve opening is linearly decreased as the
value of the input command DRCMD from the ECU 2 is increased.
Due to the above construction, in the drive pulley width variable
mechanism 26, during operation of the engine 4, the DR solenoid
valve 26b is controlled by the input command DRCMD from the ECU 2,
whereby the moving part 22a is axially actuated. As a result, the
pulley width of the drive pulley 22 is continuously changed between
a wide width for a low-speed transmission ratio shown in FIG. 3A
and a narrow width for a high-speed transmission ratio shown in
FIG. 3B. Further, when oil pressure from the DR solenoid valve 26b
to the DR oil chamber 26a is interrupted, the drive pulley 22 is
held to a pulley width at which the urging force of the return
spring and the tensile force of the belt 24 are balanced with each
other.
Further, the driven pulley 23 is constructed similarly to the drive
pulley 22. That is, the driven pulley 23 has a moving part 23a
having a truncated conical shape, and a fixed part 23b. The moving
part 23a is mounted to the counter shaft 25 such that it is axially
movable but unrotatable thereabout, while the fixed part 23b is
disposed in a manner opposed to the moving part 23a, and fixed to
the counter shaft 25. Further, opposed surfaces of the moving part
23a and the fixed part 23b are formed to provide inclined surfaces,
whereby a V-shaped belt groove for causing the belt 24 to extent
therein is formed between the moving part 23a and the fixed part
23b. The transmission belt 24 is a metal belt, and stretched around
the pulleys 22 and 23 in a state fitted in the belt grooves
thereof.
The driven pulley width variable mechanism 27 is for changing the
pulley width of the driven pulley, and constructed similarly to the
drive pulley width variable mechanism 26. That is, the driven
pulley width variable mechanism 27 includes a DN oil chamber 27a
formed within the moving part 23a, a DN solenoid valve 27b for
controlling the oil pressure supplied to the DN oil chamber 27a,
and a return spring (not shown) for urging the moving part 23a
toward the fixed part 23b.
The DN solenoid valve 27b is disposed between the oil pressure pump
28a and the DN oil chamber 27a of the moving part 23a, and
connected to them via respective oil passages 28b and 28b. This
causes, during operation of the engine 4, the oil pressure
delivered from the oil pressure pump 28a to be constantly supplied
to the DN solenoid valve 27b via the oil passage 28b. The DN
solenoid valve 27b is of a normally-open type, similarly to the DR
solenoid valve 26b, which is comprised of a combination of a
solenoid and a spool valve (neither of which is shown). When the
input command PNCMD from the ECU 2 is not supplied to the DN
solenoid valve 27b, the DN solenoid valve 27b is held in the
fully-open state to thereby supply oil pressure from the oil
pressure pump 28a to the DN oil chamber 27a via the oil passages
28b.
Due to the above construction, in the driven pulley width variable
mechanism 27, during operation of the engine 4, the DN solenoid
valve 27b is controlled by the command input DNCMD from the ECU 2,
whereby the moving part 23a is axially actuated. As a result, the
pulley width of the driven pulley 23 is continuously changed
between a narrow width for a low-speed transmission ratio shown in
FIG. 4A and a wide width for a high-speed transmission ratio shown
in FIG. 4B. Further, when the supply of the oil pressure from the
DN solenoid valve 27b to the DN oil chamber 27a is interrupted, the
driven pulley 23 is held at a pulley width at which the urging
force of the return spring and the tensile force of the belt 24 are
balanced with each other.
As described above, in the continuously variable transmission 20,
the two solenoid valves 26b and 27b are controlled by the ECU 2 to
continuously vary the pulley widths of the two pulleys 22 and 23,
whereby the transmission ratio RATIO (=NDR/NDN) defined as a ratio
of a drive-pulley rotational speed NDR of the drive pulley 22 and a
driven-pulley rotational speed NDN of the driven pulley 23 is
continuously variably controlled.
The start clutch 30 is a friction multi-plate clutch of a
hydraulically controlled type which has its engagement and
disengagement controlled by the supply of oil pressure thereto, and
is comprised of a multiplicity of inner plates 31 and a
multiplicity of outer plates 32, a clutch engagement mechanism 33
for engaging and disengaging between these plates 31 and 32, and a
return spring, not shown, for urging these plates 31 and 32 in the
direction of disengagement therebetween. These inner plates 31 are
connected to a gear 34 rotatably fitted on the counter shaft 25,
and rotate in unison with the gear 34 along with rotation thereof.
Further, the outer plates 32 are connected to the counter shaft 25,
and rotate in unison therewith along with rotation thereof.
The clutch engagement mechanism 33 is comprised of a clutch oil
chamber 33a and an SC solenoid valve 33b (control valve). As shown
in FIG. 2, the SC solenoid valve 33b is disposed between the oil
pressure pump 28a of the hydraulic circuit 28 and the clutch
chamber 33a, and connected to them via the oil passages 28b and
28b.
The SC solenoid valve 33b is of a normally-closed type which is
comprised of a combination of a solenoid and a spool valve (neither
of which is shown), and electrically connected to the ECU 2. When
the SC solenoid valve 33b has no input command SCCMD from the ECU
2, the SC solenoid valve 33b is held in the fully-closed state,
which inhibits oil pressure from the oil pressure pump 28a from
being supplied to the clutch oil chamber 33a, whereby the inner
plates 31 and the outer plates 32 are disengaged from each other by
the pressure (urging force) of the return spring. As a result, no
friction is generated between the plates 31 and 32 to thereby
hinder the rotation and torque of the counter shaft 25 from being
transmitted to the gear 34. In short, the start clutch 30 is held
in the disengaged state. Further, the SC solenoid valve 33b is
constructed as a linear solenoid valve whose valve opening is
linearly increased as the value of the input command SCCMD from the
ECU 2 is increased.
Further, the gear 34 mates with a large idler gear 35a integrally
formed with an idler shaft 35, and a small idler gear 35b
integrally formed with the idler shaft 35 mates with a gear 6a of
the differential gear mechanism 6. This causes the gear 6a to
rotate along with rotation of the gear 34.
Due to the above construction, during operation of the engine 4,
when the input command SCCMD from the ECU 2 to the SC solenoid
valve 33b, oil pressure is supplied to the clutch oil chamber 33a,
and the inner plates 31 and the outer plates 32 are engaged with
each other against the pressure of the return spring. As a result,
a frictional force is generated between the plates 31, 32 to engage
the start clutch 30, whereby the rotation and torque of the counter
shaft 25 is transferred to the drive wheels 7 and 7. In this
process, as the value of the input command SCCMD to the SC solenoid
valve 33b is increased, the valve opening of the SC solenoid valve
33b is increased to increase the oil pressure supplied to the
clutch oil chamber 33a, whereby the engagement force of the start
clutch 30 is controlled to a larger value.
Also connected to the ECU 2 are a crankshaft sensor 40 (rotational
speed parameter-detecting means), a throttle valve opening sensor
41 (vehicle start operation-detecting means), an intake pipe
absolute pressure sensor 42, an accelerator pedal opening sensor
43, a drive-pulley rotational speed sensor 44 (transmission
ratio-detecting means, and rotational speed parameter-detecting
means), a driven-pulley rotational speed sensor 45 (transmission
ratio-detecting means, and rotational speed parameter-detecting
means), an idler shaft rotational speed sensor 46 (vehicle
speed-detecting means), and a shift position sensor 47.
The crank angle sensor 40 is formed by a combination of a magnet
rotor and an MRE pickup (neither of which is shown), and delivers a
CRK signal, which is a pulse signal, to the ECU 2 along with
rotation of the crankshaft 4a. Each pulse of the CRK signal is
generated whenever the crankshaft 4a rotates through a
predetermined crank angle (e.g. 30 degrees), and the ECU 2
calculates the rotational speed NE (rotational speed parameter) of
the engine 4 (hereafter referred to as "the engine speed") based on
the CRK signal.
The throttle valve opening sensor 41 detects the throttle valve
opening TH (result of detection by the vehicle start
operation-detecting means); the intake pipe absolute pressure
sensor 42 detects an intake pipe absolute pressure PBA which is the
absolute pressure within the intake pipe (not shown) of the engine
4; and the accelerator pedal opening sensor 43 detects the
accelerator pedal opening AP, which is a degree of opening i.e.
stepped-on amount of an accelerator pedal, not shown, of the
vehicle 3. Respective signals indicative of detected parameters of
operating conditions of the engine 4 are delivered to the ECU
2.
Further, the drive-pulley rotational speed sensor 44 detects the
drive-pulley rotational speed NDR (rotational speed parameter),
which is the rotational speed of the drive pulley 22; the
driven-pulley rotational speed sensor 45 detects the driven-pulley
rotational speed NDN (rotational speed parameter), which is the
rotational speed of the driven pulley 23; and the idler shaft
rotational speed sensor 46 detects an idler shaft rotational speed
NDI, which is the rotational speed of the idler shaft 35.
Respective signals indicative of the rotational speeds detected by
these sensors are delivered to the ECU 2. The ECU 2 calculates the
transmission ratio RATIO (rotational speed parameter) based on the
drive-pulley rotational speed NDR and the driven-pulley rotational
speed NDN. Further, the ECU 2 calculates a slip ratio ESC (%) which
is a ratio between the input-side rotational speed and output-side
rotational speed of the start clutch 30 based on the drive-pulley
rotational speed NDN and the idler shaft rotational speed NDI, and
also calculates the vehicle speed VP based on the idler shaft
rotational speed NDI.
The shift position sensor 47 detects a position of a shift lever,
not shown, in one of six shift ranges: D-range, R-range, N-range,
D-range, S(sports)-range, and L-range, and delivers a signal POSI
indicative of the detected position of the shift lever to the ECU
2. The S-range is for the forward travel, and when the shift lever
is in the S-range, the transmission ratio RATIO is controlled to a
value slightly higher than when the same is in the D-range.
The ECU 2 is implemented by a microcomputer comprised of a CPU, a
RAM, a ROM, and an input/output interface, none of which are shown.
The ECU 2 determines whether or not a failure of any of the
solenoid valves 26b, 27b, and 33b has occurred, as described
hereinafter, based on the signals inputted from the above sensors
40 to 47. In the present embodiment, the transmission
ratio-detecting means, the vehicle speed-detecting means,
failure-determining means, the vehicle start operation-detecting
means, torque-detecting means, and the rotational speed
parameter-detecting means are implemented by the ECU 2.
Although not shown, the ECU 2 controls the operating condition of
the engine 4, the connected state of the forward/backward
travel-switching mechanism 10, the speed varying operation of the
continuously variable transmission 20, the engaged state of the
start clutch 30, the throttle valve opening TH, and so forth. For
example, during stoppage of the vehicle 3, the transmission ratio
RATIO is controlled to a value within a predetermined LOW
(low-speed)-side range (range of
RTDRDNBL.ltoreq.RATIO.ltoreq.RTDRDNBH, referred to hereinafter,
e.g. a range of 2.0 through 2.5). Further, during travel of the
vehicle 3, a target transmission ratio RATTGT is calculated based
on the vehicle speed VP and the throttle valve opening TH, and the
speed varying operation of the continuously variable transmission
20 is controlled such that the transmission ratio RATIO becomes
equal to the target transmission ratio RATTGT. As a result, when
the vehicle 3 is traveling, the transmission ratio RATIO is
controlled to a value within a predetermined range (e.g. 0.4 to
2.5).
Further, the ECU 2 controls the engagement force of the start
clutch 30 based on the operating conditions of the engine 4, the
state of the speed varying operation of the continuously variable
transmission 20, and so forth. Further, when the vehicle 3 is
standing with the engine 4 operating, the forward/backward
travel-switching mechanism 10 is controlled such that the torque of
the engine 4 is transferred to the continuously variable
transmission 20, and the start clutch 30 is controlled to be
disengaged. As a result, even when the vehicle 3 is standing, the
drive pulley 22 and the driven pulley 23 rotate, so that the
transmission ratio RATIO is calculated.
It should be noted that the RAM of the ECU 2 is comprised of an
ordinary RAM which has data stored therein erased when the supply
of electric power is interrupted after the stop of the engine 4,
and a backup RAM which holds data stored therein even after the
stop of the engine 4, due to power supply from a backup power
source.
Next, a solenoid valve monitoring process carried out by the ECU 2
will be described with reference to FIG. 5. The solenoid valve
monitoring process is performed to determine whether or not any of
the DR solenoid valve 26b, the DN solenoid valve 27b, and the SC
solenoid valve 33b has failed, i.e. is faulty, and executed
whenever a predetermined time period (e.g. 100 msec.) elapses.
As shown in FIG. 5, in this process, first, in a step 1 (in FIG. 5,
abbreviated to S1; this rule also applies to the other steps
referred to hereinafter), an executable condition determining
process is carried out. This process is performed to determine
whether or not conditions for executing the solenoid valve failure
determination are satisfied, which will be described in detail
hereinafter.
Then, in a step 2, a travel incapability determining process is
carried out. This process is for determining whether or not the
vehicle 3 is incapable of traveling, and details thereof will be
described hereinafter.
Next, in a step 3, a fixation determining process for determining
fixation of the SC solenoid valve 33b is carried out. This process
is for determining whether or not the SC solenoid valve 33b is
fixed in the fully-closed state, and details thereof will be
described hereinafter.
Then, in a step 4, a fixation determining process for determining
whether any of the DR solenoid valve 26b and the DN solenoid valve
27b is fixed is carried out. This process is for determining
whether or not any of the solenoid valves 26b and 27b is fixed in
the fully-open state or in the fully-closed state, and details
thereof will be described hereinafter. After that, the solenoid
valve monitoring process is terminated.
Next, the executable condition determining process carried out in
the step 1 will be described with reference to FIG. 6. In this
process, first, in a step 10, it is determined whether or not a
sensor normality flag F_SENSEROK is equal to 1. The sensor
normality flag F_SENSEROK is set to 1 when it is determined that
all of the above-mentioned sensors 40 to 47 are normal, and
otherwise set to 0.
If the answer to the above question is affirmative (YES), i.e. if
all of the above-mentioned sensors 40 to 47 are normal, the process
proceeds to a step 11, wherein it is determined whether or not the
engine rotational speed NE is equal to or higher than a
predetermined reference value NESOLMON. This determination is
carried out to determine whether or not the engine 4 is in
operation. To this end, the reference value NESOLMON is set to a
value (e.g. 500 rpm) at which the engine 4 can be positively
presumed to be in operation.
If the answer to the question of the step 11 is affirmative (YES),
i.e. if the engine 4 is in operation, the process proceeds to a
step 12, wherein it is determined whether or not an INGEAR flag
F_FCLE is equal to 1. The INGEAR flag F_FCLE is set to 1 when the
rotation of the engine 4 is transmitted to the main shaft 21, that
is, to the drive pulley 22 via the forward/backward
travel-switching mechanism 10 described hereinabove, and otherwise
set to 0. More specifically, the INGEAR flag F_FCLE is set by
comparing the difference between the engine rotational speed NE and
the drive-pulley rotational speed NDR with a predetermined
value.
If the answer to the question of the step 12 is affirmative (YES),
i.e. if the rotation of the engine 4 is transmitted to the drive
pulley 22 via the forward/backward travel-switching mechanism 10,
it is judged that the conditions for executing the failure
determination of the solenoid valves are satisfied, so that the
process proceeds to a step 13, wherein an executable condition flag
F_SOLMONEN is set to 1 to indicate the fact, followed by
terminating the present process.
On the other hand, if any of the answers to the questions of the
steps 10 to 12 is negative (NO), i.e. if any of the sensors 40 to
47 has failed, if the engine 4 is in stoppage, or if the rotation
of the engine 4 is not transmitted to the drive pulley 22 via the
forward/backward travel-switching mechanism 10, it is judged that
the conditions for executing the failure determination of the
solenoid valves are not satisfied, and the process proceeds to a
step 14, wherein the executable condition flag F_SOLMONEN is set to
0 to indicate the fact, followed by terminating the present
process.
Next, the travel incapability determining process in the step 2
will be described with reference to FIG. 7. In this process, first,
it is determined in a step 20 whether or not a first travel
incapability reference value NERUNNG is calculated by a TH-NERUNNG
table shown in FIG. 8 according to the throttle valve opening TH.
The first travel incapability reference value NERUNNG is for
discriminating between a hill-climbing state of the vehicle 3 and a
state of the same incapable of travel due to failure of the SC
solenoid valve 33b. That is, when the vehicle 3 is climbing a hill,
the throttle valve opening TH and a target clutch pressure PCCMD
both become high, so that answers to questions of steps 25 and 26,
referred to hereinafter, can both become affirmative. Therefore, to
discriminate such a hill-climbing state of the vehicle 3 from
failure of the SC solenoid value 33b, the first travel incapability
reference value NERUNNG is compared with the engine speed NE in a
step 28, referred to hereinafter. Further, as shown in FIG. 8, in
this table, the first travel incapability reference value NERUNNG
is set to a larger value as the throttle valve opening TH is
larger. This is because the engine speed NE rises to a higher value
as the throttle valve opening TH is larger.
Next, the process proceeds to a step 21, wherein a second travel
incapability reference value PCRUNNG is calculated by. searching a
TH-PCRUNNG table according to the throttle valve opening TH. The
second travel incapability reference value PCRUNNG (defining a
predetermined range of the input command) is compared with the
target clutch pressure PCCMD in a step 27, referred to hereinafter,
and as shown in FIG. 9, in this table, the second travel
incapability reference value PCRUNNG is set to a larger value as
the throttle valve opening TH is larger. This is because as the
throttle valve opening is larger, the engine torque becomes larger,
causing the target clutch pressure PCCMD to be set to a higher
value.
Then, the process proceeds to a step 22, wherein it is determined
whether or not the executable condition flag F_SOLMONEN is equal to
1. If the answer to this question is affirmative (YES), which means
that the conditions for executing the solenoid valve failure
determination are satisfied, the process proceeds to a step 23,
wherein it is determined whether or not the driven-pulley
rotational speed NDN is higher than a predetermined reference value
NDNREF. This determination is for determining whether the driven
pulley 23 is rotating, and to this end, the reference value NDNREF
is set to a value (e.g. 3 rpm) at which the driven pulley can be
positively presumed to be rotating.
If the answer to the question of the step 23 is affirmative (YES),
which means that the driven pulley 23 is rotating, the process
proceeds to a step 24, wherein it is determined whether or not the
shift lever is in the D-range or S-range. If the answer to this
question is affirmative (YES), the process proceeds to a step 25,
wherein it is determined whether or not the vehicle speed VP is
lower than a predetermined reference value VRUNNG. This
determination is for determining whether or not the vehicle 3 is
standing. To this end, the reference value VRUNNG is set to a value
(e.g. 3 km/h) at which the vehicle 3 can be positively presumed to
be standing.
If the answer to this question is affirmative (YES), which means
that the vehicle 3 is standing, the process proceeds to a step 26,
wherein it is determined whether or not the throttle valve opening
TH is equal to or larger than a predetermined reference value THRUN
(e.g. 6.25%). If the answer to this question is affirmative (YES),
which means the accelerator pedal is stepped on by the driver,
causing the throttle valve opening TH to be larger than the
reference value THRUN, the process proceeds to a step 27, wherein
it is determined whether or not the target clutch pressure PCCMD is
equal to or higher than the second travel incapability reference
value PCRUNNG.
This target clutch reference value PCCMD (corresponding the input
command) is a target value of oil pressure to be supplied to the
clutch chamber 33a via the SC solenoid valve 33b for control of the
engaging force of the start clutch 30, and the command input SCCMD
to the SC solenoid valve 33b is set based on the target clutch
pressure PCCMD. More specifically, the input command SCCMD is set
to a larger value as the target clutch pressure PCCMD is higher,
whereby the degree of valve opening of the SC solenoid valve 33b is
controlled to a larger value, thereby controlling the engaging
force of the start clutch 30 to a larger value. It should be noted
that the target clutch pressure PCCMD is set to a value obtained by
adding the pressure of return spring to the product of the engine
torque PME, the transmission ratio RATIO, and a predetermined
coefficient. The engine torque PME is determined based on the
engine speed NE and the intake pipe absolute pressure PBA (or the
throttle valve opening TH).
If the answer to the question of the step 27 is affirmative (YES),
i.e. if PCCMD.gtoreq.PCRUNNG holds, which means that the input
command SCCMD to the SC solenoid valve 33b is set to a
predetermined value or higher, the process proceeds to a step 28,
wherein it is determined whether or not the engine speed NE is
equal to or higher than the first travel incapability reference
value NERUNNG. If the answer to this question is affirmative, i.e.
if NE.gtoreq.NERUNNG holds, it is provisionally determined that the
vehicle 3 is not climbing a hill, but is incapable of traveling
because of the failure of the SC solenoid valve 33b, so that the
process proceeds to a step 29, wherein to indicate the provisional
determination, a travel incapability provisional determination flag
F_RUNNGZN is set to 1.
Then, the process proceeds to a step 30, wherein a counter value
RUNNGCON of a travel incapability provisional determination counter
is incremented by 1. Thereafter, the process proceeds to a step 31,
wherein it is determined whether or not the counter value RUNNGCON
is equal to or larger than a predetermined reference value RUNNGJD
(e.g. 200). If the answer to this question is affirmative (YES),
which means that the state in which the vehicle 3 is incapable of
traveling is detected or provisionally determined a predetermined
number (equal to the reference value RUNNGJD) of times or more, it
is finally determined that the vehicle 3 is incapable of traveling,
so that the process proceeds to a step 32, wherein to indicate the
determination, a travel incapability determination flag F_RUNNGJD
is set to 1, followed by terminating the present process.
On the other hand, if the answer to the question of the step 31 is
negative (NO), which means that the counter value RUNNGCON has not
reached the predetermined reference value RUNNGJD, the process
proceeds to a step 35, wherein the travel incapability
determination flag F_RUNNGJD is set to 0, followed by terminating
the present process.
Further, if any of the answers to the questions of the steps 22 to
24, and 26 to 28 is negative (NO), i.e. if the conditions for
executing the solenoid valve failure determination are not
satisfied, if the driven-pulley 23 is in stoppage, if the shift
lever is neither is the D-range nor in the S-range, if the throttle
valve opening TH is smaller than the reference value THRUN, if the
target clutch pressure PCCMD is lower than the second travel
incapability reference value PCRUNNG, or if the engine speed NE is
lower than the first travel incapability reference value NERUNNG,
as well, the step 35 is executed, followed by terminating the
present process.
On the other hand, if the answer to the question of the step 25 is
negative (NO), which means that the vehicle 3 is traveling, the
process proceeds to a step 33, wherein the counter value RUNNGCON
of the travel incapability provisional determination counter is
reset to 0, and then in a step 34, the travel incapability
determination reference flag F_RUNNGJD is set to 0. Thereafter, the
step 35 is executed, followed by terminating the present
process.
Next, the fixation determination process for determining fixation
of the SC solenoid valve 33b executed in the step 3 will be
described with reference to FIG. 10. In this process, first, in a
step 40, it is determined whether or not the executable condition
flag F_SOLMONEN is equal to 1. If the answer to this question is
affirmative (YES), which means that the conditions for executing
the solenoid valve failure determination are satisfied, the process
proceeds to a step 41, wherein it is determined whether or not the
shift lever is in the D-range or S-range.
If the answer to this question is affirmative (YES), i.e. if the
shift lever is in the D-range or S-range, the process proceeds to a
step 42, wherein it is determined whether or not the travel
incapability determination flag F_RUNNNGJD is equal to 1. If the
answer to this question is affirmative (YES), which means that the
vehicle 3 is incapable of traveling, the process proceeds to a step
43, wherein to indicate the fact that the SC solenoid valve 33b is
fixed in the fully-closed state, an SC solenoid valve failure flag
F_FSKSC is set to 1.
Then, the process proceeds to a step 44, wherein an SC solenoid
normality flag F_OKSC for indication of normality of the SC
solenoid valve 33b is set to 0, and then proceeds to a step 45,
wherein a counter value CTOKSC of a normality provisional
determination counter, referred to hereinafter, is reset to 0.
Then, the process proceeds to a step 46, wherein a
post-determination process is executed. In this process, the values
of the SC solenoid valve failure flag F_FSCKS and the solenoid
valve normality flag F_OKSC are written in the backup RAM, followed
by terminating the present process.
On the other hand, if the answer to the question of the step 42 is
negative (NO), i.e. if the vehicle 3 is capable of traveling, the
process proceeds to a step 47, wherein it is determined whether or
not the vehicle speed VP is equal to or higher than a SC normality
reference value VSCOK (e.g. 40 km/h). If the answer to this
question is affirmative (YES), which means that the vehicle speed
VP is sufficiently high, the process proceeds to a step 48, wherein
it is determined whether or not the throttle valve opening TH is
equal to or larger than an SC reference value THSCOK (e.g. 5%).
If the answer to this question is affirmative (YES), which means
that the throttle valve is open, the process proceeds to a step 49,
wherein an SC normality reference value THSCOFOK is calculated by
searching an NE-THSCOFOK table according to the engine speed NE.
The SC normality reference value THSCOFOK is for determining
normality determination of the SC solenoid valve 33b, and as shown
in FIG. 11, in this table, the SC normality reference value
THSCOFOK is set to a larger value as the engine speed NE is higher.
This is because in the control of the throttle valve, as the engine
speed NE is higher, the throttle valve opening TH is set to a
larger value.
Then, the process proceeds to a step 50, wherein it is determined
whether or not the throttle valve opening TH is smaller than the SC
normality reference value THSCOFOK. If the answer to this question
is affirmative (YES), it is judged that the SC solenoid valve 33b
cannot be regarded as normal, so that the process proceeds to the
step 45, wherein the counter value CTOKSC of the normality
provisional determination counter is reset to 0. Then, the step 46
is executed, followed by terminating the present process.
On the other hand, if the answer to the question of the step 50 is
negative (NO), it is judged that the SC solenoid valve 33b can be
regarded as normal, so that the process proceeds to a step 53,
wherein to indicate the fact, the SC solenoid valve failure flag
F_FSKSC is set to 0. Then, the process proceeds to a step 54,
wherein the counter value CTOKSC of the normality provisional
determination counter is incremented by 1.
Then, the process proceeds to a step 55, wherein it is determined
whether or not the counter value CTOKSC is equal to or larger than
a predetermined normality reference value CTOKREF (e.g. 500). If
the answer to this determination is negative (NO), the step 46 is
executed, followed by terminating the present process, whereas if
the answer is affirmative (YES), which means that a state in which
the SC solenoid valve 33b can be regarded as normal has continued
for a predetermined time period or longer, the process proceeds to
a step 56, wherein to indicate that the SC solenoid valve 33b is
normal, the SC solenoid normality flag F_OKSC is set to 1, and then
the step 46 is executed, followed by terminating the present
process.
On the other hand, if the answer to the question of the step 48 is
negative (NO), i.e. if the throttle valve is almost closed, the
process proceeds to a step 51, wherein it is determined whether or
not a deceleration F/C flag F_DECFC is equal to 1. The deceleration
F/C flag F_DECFC is set to 1 when the fuel cut operation is being
carried out during deceleration, and otherwise set to 0.
If the answer to this question is affirmative (YES), which means
that the F/C operation is being carried out during deceleration,
the process proceed to a step 52, wherein it is determined whether
or not the slip ratio ESC of the start clutch 30 is equal to or
higher than a predetermined lower limit value ESCOKL (e.g. 95%),
and at the same time equal to or lower than a predetermined upper
limit value (e.g. 105%). If the answer to this question is
affirmative (YES), which means that the start clutch 30 scarcely
slips, it is judged, similarly to the case of the answer to the
question of the step 50 being negative (NO), that the SC solenoid
valve 33b can be regarded as normal, so that the process proceeds
to the step 53, wherein to indicate the fact, the SC solenoid valve
failure flag F_FSKSC is set to 0. Then, the step 54 et seq. are
executed as described hereinabove, followed by terminating the
present process.
On the other hand, if any of the answers to the questions of the
step 47, 51, and 52 is negative (NO), i.e. if the vehicle speed VP
is not sufficiently high, if the F/C operation is not being
performed during deceleration, if the start clutch 30 slips too
much, or if the vehicle is being engine-braked, the process
proceeds to a step 57, wherein similarly to the step 45, the
counter value CTOKSC of the normality provisional determination
counter is reset to 0. Then, the step 46 is executed, followed by
terminating the present process.
If either of the answers to the questions of the steps 40 and 41 is
negative (NO), i.e. if the conditions for executing the solenoid
valve failure determination are not satisfied, or if the shift
lever is neither in the D-range nor in the S-range, the steps 45
and 46 are executed, followed by terminating the present
process.
As described above, in the travel incapability determining process
shown in FIG. 7 and the fixation determining process for the SC
solenoid valve 33b shown in FIG. 10, on condition that the driven
pulley 23 is rotating, that the shift lever is in the D-range or
S-range, that the vehicle 3 is standing, that the throttle valve is
sufficiently wide open, that the input command SCCMD to the SC
solenoid valve 33b is large, and that the engine speed NE is high,
it is determined that the vehicle 3 is incapable of traveling
(F_RUNNGJD.rarw.1), and at the same time, when such a determination
that the vehicle 3 is incapable of traveling is made, it is
determined that the SC solenoid valve 33b is fixed in the
fully-closed state. This is for the following reason:
Firstly, since the driven pulley 23 is rotating, it is presumed
that the torque is transferred to the start clutch 30. In this
state, assuming that the SC solenoid valve 33b is normal, as
indicated by curves of broken lines in FIG. 12, when the
accelerator pedal is stepped on at the standing start of the
vehicle 3, causing the throttle valve TH to increase, the engine
speed NE and the target clutch pressure PCCMD both increase, and
the vehicle speed VP increases accordingly.
In contrast, if the SC solenoid valve 33b is fixed in the
fully-closed state, as shown in curves of solid lines in FIG. 12,
when the accelerator pedal is stepped on to cause the throttle
valve TH to increase, in spite of the fact that the engine speed NE
and the target clutch pressure PCCMD both rise to values higher
than those assumed when the SC solenoid valve 33b is normal, the
vehicle speed VP remains equal to 0, i.e. the vehicle 3 is
standing. In other words, even if the supply of oil pressure from
the hydraulic circuit 28 is short, in spite of the fact that the
target clutch pressure PCCME has risen to a value high enough to
provide the sufficiently strong engaging force of the start clutch
30 enabling the vehicle 3 to make a standing start, in other words,
in spite of the input command SCCMD being large enough, the vehicle
is still standing. Therefore, it can be determined that the SC
solenoid valve 33b is fixed in the fully-closed state, causing the
disengaged state of the start clutch 30, which inhibits the engine
torque from being transferred to the drive wheels 7. Further, when
the vehicle 3 is climbing a hill, the throttle valve opening TH
becomes large, and the target clutch pressure PCCMD becomes high.
However, the engine speed NE does not rise so high as in the case
of the fixation of the SC solenoid valve 33b, which makes it
possible to discriminate the two cases from each other. Thus, based
on the various conditions described above, it is possible to
determine whether or not the SC solenoid valve 33b is fixed in the
fully-closed state.
As described above, according to the failure determination system 1
of the present embodiment, based on the various conditions
described above, it is possible to determine whether or not the SC
solenoid valve 33b is fixed in the fully-closed state, irrespective
of shortage of supply of oil pressure from the hydraulic circuit
28, and identify the failure of the SC solenoid valve 33b. As a
consequence, it is possible to easily repair the start clutch 30
simply by replacing the SC solenoid valve 33b, and thereby improve
maintainability thereof.
Next, the fixation determining process for determining whether any
of the DR solenoid valve 26b and the DN solenoid valve 27b is
fixed, executed in the step 4 will be described with reference to
FIG. 13. In this process, first, a stop-time transmission ratio
determining process is carried out in a step 120.
Referring to FIG. 14, in the stop-time transmission ratio
determining process, first, in a step 130, it is determined whether
or not a rapid deceleration-time determination inhibition flag
F_IGDJDAB is equal to 0. The rapid deceleration-time determination
inhibition flag F_IGDJDAB is set to 1 when the vehicle 3 is being
rapidly decelerated, and otherwise set to 0. More specifically, the
rapid deceleration-time determination inhibition flag F_IGDJDAB is
set based on the drive-pulley rotational speed NDR, and the
difference between the immediately preceding value and present
value of vehicle speed VP (i.e. acceleration).
If the answer to the above question is affirmative (YES), i.e. if
the vehicle 3 is not being rapidly decelerated, it is judged that
the stop-time transmission ratio determining process should be
executed, so that the process proceeds to a step 131, wherein it is
determined whether or not the vehicle speed VP is lower than a
predetermined stop-time reference value VINGRTJD. The stop-time
reference value VINGRTJD is set to a value at which the
transmission ratio RATIO can be positively presumed to have
returned to a LOW side thereof if both of the solenoid valves 26b
and 27b are normal.
If the answer to the above question is affirmative (YES), i.e. if
the vehicle 3 is standing, the process proceeds to a step 132,
wherein it is determined whether or not the throttle valve opening
TH is smaller than a predetermined stop-time reference value
THINGRTJD. The stop-time reference value THINGRTJD is for
determining whether or not the throttle valve is in the closed
state, i.e. whether or not the accelerator pedal is not stepped on,
and set to a value (e.g. 5%) at which the throttle valve is
expected to be closed.
If the answer to the above question is affirmative (YES), i.e. if
the throttle valve is in the closed state, the process proceeds to
a step 133, wherein it is determined whether or not the executable
condition flag F_SOLMONEN is equal to 1. If the answer to this
question is affirmative (YES), i.e. if the conditions for executing
the solenoid valve failure determination are satisfied, the process
proceeds to a step 134, wherein it is determined whether or not the
position of the shift lever is in the D-range or S-range.
If the answer to this question is affirmative (YES), the process
proceeds to a step 135, wherein it is determined whether or not the
transmission ratio RATIO is in a predetermined stop-time LOW-side
range. More specifically, the stop-time LOW-side range is set to a
range between a LOW-side lower limit value RTINGLOL (e.g. 1.8) and
a LOW-side higher limit value RTINGLOH (e.g. 2.5), which is the
same range as a LOW-side range applied to the fixation determining
process, referred to hereinafter. If the answer to the above
question is affirmative (YES), i.e. if
RTINGLOL.ltoreq.RATIO.ltoreq.RTINGLOH holds, the process proceeds
to a step 136, wherein it is determined whether or not a timer
value TMLOJDWT of a delay timer is equal to 1.
The delay timer is of a downcount type whose timer value TMLOJDWT
is set to 0 as an initial value at the start of the engine 4, and
as described hereinafter, set to a predetermined value TMLOREF
(e.g. 2.0 sec) when a stop-time OD-side flag F_INGODJD is equal to
1. The delay timer is used for the following reason: Immediately
after the accelerator pedal is suddenly stepped on to cause the
belt 24 to slip between the pulleys 22 and 23, if the accelerator
pedal is released, the transmission ratio RATIO can temporarily
fall within the stop-time LOW-side S-range, so that there is a fear
of being erroneously determined that the transmission ratio RATIO
is within the stop-time LOW-side range although actually not in the
range. To prevent such an erroneous determination, the delay timer
is used.
If the answer to the question of the step 136 is negative (NO),
i.e. if the delay timer has not completed counting of the
predetermined value TMLOREF, it is judged that there is a fear of
the erroneous determination, and hence the present process is
immediately terminated. On the other hand, if the answer to the
question of the step 136 is affirmative (YES), i.e. if the delay
timer has completed counting of the predetermined value TMLOREF, it
is judged that the transmission ratio RATIO is in the stop-time
LOW-side range, and to indicate the fact, in a step 137, the
stop-time OD-side flag F_INGODJD is set to 0, and in a step 138, a
stop-time LOW-side flag F_INGLOWJD is set to 1, followed by
terminating the present process.
On the other hand, if the answer to the question of the step 135 is
negative (NO), i.e. if the transmission ratio RATIO is not in the
stop-time LOW-side range, the process proceeds to a step 139,
wherein it is determined whether or not the transmission ratio
RATIO is within a predetermined stop-time OD-side range. The
stop-time OD(high-speed)-side range) is a range on the OD-side
lower than the above stop-time LOW-side range. More specifically,
the stop-time OD-side range is set to a range between a lower limit
value RTINGODL (e.g. 0.3) and a predetermined upper limit value
RTINGODH (e.g. 0.8).
If the answer to this question is affirmative (YES), i.e. if
RTINGODL.ltoreq.RATIO.ltoreq.RTINGODH holds, it is judged that the
transmission ratio RATIO is within the stop-time OD-side range, and
to indicate the fact, in a step 140, the stop-time OD-side flag
F_INGODJD is set to 1, and in a step 141, the stop-time LOW-side
flag F_INGLOWJD is set to 0.
Then, the process proceeds to a step 142, wherein it is determined
whether or not the stop-time OD-side flag F_INGODJD is equal to 1.
If the answer to this question is negative (NO), the present
process is immediately terminated. On the other hand, if the answer
to the question is affirmative (YES), the process proceeds to a
step 143, wherein the timer value TMLOJDWT of the delay timer is
set to the predetermined value TMLOREF for the above-described
reason, followed by terminating the present process.
On the other hand, if any of the answers to the questions of the
steps 133, 134, and 139 is negative (NO), i.e. if the conditions
for executing the solenoid valve failure determination are not
satisfied, if the position of the shift lever is in a range other
than the D-range and S-range, or if the transmission ratio RATIO is
neither in the stop-time LOW-side range nor in the stop-time
OD-side range, the process proceeds to a step 144, wherein the
stop-time LOW-side flag F_INGLOWJD is set to 0. Then, the step 142
et seq. are carried out as described hereinabove, followed by
terminating the present process.
On the other hand, if any of the answers to the questions of the
steps 130 to 132 is negative (NO), i.e. if the vehicle 3 is being
rapidly decelerated, if the vehicle 3 is not standing, or if the
accelerator pedal is stepped on to thereby cause the throttle valve
to be open, the step 144 is executed, and then the step 142 et seq.
are carried out as described above, followed by terminating the
present process.
As described hereinabove, in the stop-time transmission ratio
determining process, the values of the stop-time OD-side flag
F_INGODJD and the stop-time LOW-side flag F_INGLOWJD are set.
Referring again to FIG. 13, in a step 121 following the step 120,
it is determined whether or not the executable condition flag
F_SOLMONEN is equal to 1. If the answer to this question is
affirmative (YES), i.e. if the conditions for executing the
solenoid valve failure determination are satisfied, the process
proceeds to a step 122, wherein it is determined whether or not the
position of the shift lever is in the D-range or S-range. If the
answer to this question is affirmative (YES), the process proceeds
to a step 123, wherein it is determined whether or not the
stop-time OD-side flag F_INGODJD is equal to 1.
If the answer to this question is affirmative (YES), which means
that the transmission ratio RATIO during stoppage of the vehicle 3
was within the stop-time OD-side range, the process proceeds to a
step 124, wherein an OD-side determining process is carried out, as
will be described hereinafter. On the other hand, if the answer to
the above question is negative (NO), which means that the
transmission ratio RATIO during stoppage of the vehicle 3 was not
within in the stop-time OD-side range, the process proceeds to a
step 125, wherein a LOW-side determining process is carried out, as
will be described hereinafter.
In a step 126 following the step 124 or the step 125, a
post-determination process is executed. In the post-determination
process, the values of the flags set by the stop-time transmission
ratio determining process, and the OD-side determining process or
the LOW-side determining process are stored in the backup RAM,
followed by terminating the present process.
Next, the OD-side determining process carried out in the step 124
will be described with reference to FIGS. 15 and 16. This process
is carried out to determine whether or not the DR solenoid valve
26b is fixed in the fully-open state, and/or whether or not the DN
solenoid valve 27b is fixed in the fully-closed state. More
specifically, the OD-side determining process is carried out as
follows:
First, in a step 150 shown in FIG. 15, a timer value TMDRDNBJD of a
LOW-side determination timer of an upcount type is set to a value
of 0. The LOW-side determination timer will be described
hereinafter.
Then, the process proceeds to a step 151, wherein it is determined
whether or not the throttle valve opening TH is equal to or larger
than a predetermined OD-side reference value THDRDNJD (e.g. 5%). If
the answer to this question is negative (NO), i.e. if the
accelerator pedal is not stepped on by the driver, causing the
throttle valve to be substantially fully closed, the process
proceeds to a step 168, wherein a timer value TMDRDNJ2 of a second
OD-side determination timer of the upcount type is set to 0.
Then, the process proceeds to a step 169 in FIG. 16, wherein a
timer value TMDRDNJD of a first OD-side determination timer of the
upcount type is set to 0. Then, the process proceeds to a step 157,
wherein a timer value CTOKDRNS of a DRDN normality provisional
determination counter is set to 0, followed by terminating the
present process.
On the other hand, if the answer to the question of the step 151 is
affirmative (YES), i.e. if the accelerator pedal is stepped on by
the driver, causing the throttle valve to be open, the process
proceeds to a step 152, wherein it is determined whether or not the
vehicle speed VP is lower than a predetermined OD-side reference
value VDRDNJD (second predetermined vehicle speed, e.g. 15
km/h).
If the answer to this question is affirmative (YES), i.e. if the
vehicle speed VP is low, the process proceeds to a step 153,
wherein it is determined whether or not the transmission ratio
RATIO is equal to or higher than a predetermined DN-side reference
value RTDNJD. This determination is for determining whether or not
a significant slippage of the belt 24 is occurring. To this end,
the DN-side reference value RTDNJD (low-speed transmission ratio)
is set to a value (e.g. 3.0) indicative of occurrence of a
significant slippage of the belt 24. If the answer to this question
is affirmative (YES), it is regarded that the DN solenoid valve 27b
is fixed in the fully-closed state, causing a significant slippage
of the belt 24, so that the process proceeds to a step 154 in FIG.
16, wherein it is determined whether or not the timer value
TMDRDNJD of the first OD-side determination timer of the upcount
type is equal to or larger than a predetermined DN-side reference
value TDNJD (corresponding to e.g. 0.2 seconds).
If the answer to this question is affirmative (YES), i.e. if a
state where the significant slippage of the belt 24 is occurring
has continued for a predetermined time period corresponding to the
predetermined DN-side reference value TDNJD or longer, it is judged
that the DN solenoid valve 27b is fixed in the fully-closed state,
so that the process proceeds to a step 155, wherein to indicate the
fact, an OD-time DN-side failure flag F_FSKDN is set to 1, and at
the same time an OD-time DR-side failure flag F_FSKDR, a LOW-time
DRDN failure flag F_FSKDRDNB, and an OD-time DRDN failure flag
F_FSKDRDNC are all set to 0.
Then, the process proceeds to a step 156, wherein an OD-time
DN-side normality flag F_OKDN, an OD-time DR-side normality flag
F_OKDR, a LOW-time DRDN normality flag F_OKDRDNB, and an OD-time
DRDN normality flag F_OKDRDNC are all set to 0. Then, the step 157
is carried out, as described above, followed by terminating the
present process.
Referring again to FIG. 15, if either of the answers to the
questions of the steps 152 and 153 is negative (No), i.e. if the
vehicle speed VP is relatively high, or if the transmission ratio
RATIO does not assume a value indicative of occurrence of a
significant slippage of the belt 24, the process proceeds to a step
158, wherein the value of an OD-time DR-side reference torque
TQDRJD (predetermined torque) is calculated by searching a map
shown in FIG. 17 according to the engine rotational speed NE and
the transmission ratio RATIO.
As described hereinafter, the OD-time DR-side reference torque
TQDRJD is for comparison with engine torque TQEG (torque from the
drive source), and set, with respect to the engine rotational speed
NE and the transmission ratio RATIO, to a slightly larger value
than the upper limit value of the engine torque TQEG transferable
when the continuously variable transmission 20 is faulty. In FIG.
17, six values NE1 to NE6 of the engine rotational speed NE are set
such that they have a relationship of
NE1<NE2<NE3<NE4<NE5<NE6. Further, the OD-time
DR-side reference torque TQDRJD is set to a larger value as the
engine rotational speed NE is higher or as the transmission ratio
RATIO is smaller (i.e. as the transmission ratio RATIO is more
toward the OD side). This is because as the engine rotational speed
NE is higher or as the transmission ratio RATIO is more toward the
OD side, the slippage of the belt 24 is harder to occur, even when
the engine torque TQEG generated by the engine 4 is large.
Next, the process proceeds to a step 159, wherein it is determined
whether or not the engine torque TQEG is equal to or larger than
the OD-time DR-side reference torque TQDRJD set in the step 158.
The engine torque TQEG is calculated according to the engine
rotational speed NE and the intake pipe absolute pressure PBA. If
the answer to this question is affirmative (YES), i.e. if
TQEG.gtoreq.TQDRJD holds, which means that the slippage of the belt
24 is expected to occur owing to the significant engine torque
TQEG, the process proceeds to a step 160, wherein it is determined
whether or not the throttle valve opening TH is equal to or larger
than an OD-time DR-side reference value THDRJD (e.g. 37.5%).
If the answer to this question is affirmative (YES), i.e. if
TH.gtoreq.THDRJD holds, which means that the throttle valve opening
TH is considerably large, the process proceeds to a step 161,
wherein it is determined whether or not the transmission ratio
RATIO is smaller than a predetermined OD-time DR-side reference
value RTDRJD (e.g. 1.8).
If the answer to this question is affirmative (YES), i.e. if
RATIO<RTDRJD holds, which means that the belt 24 is not slipping
although both of the engine torque TQEG and the throttle valve
opening TH are considerably large, the process proceeds to a step
162 in FIG. 16, wherein it is determined whether or not the timer
value TMDRDNJD of the first OD-side determination timer is equal to
or larger than a predetermined DR-side reference value TDRJD
(corresponding to e.g. 10 seconds).
If the answer to this question is affirmative (YES), i.e. if a
state in which the belt 24 is not slipping although both of the
engine torque TQEG and the throttle valve opening TH are
considerably large has continued for a predetermined time period
corresponding to the predetermined DR-side reference value TDRJD or
longer, it is judged that the DR solenoid valve 26b is fixed in the
fully-open state, so that the process proceeds to a step 163,
wherein to indicate the fact, the OD-time DR-side failure flag
F_FSKDR is set to 1, and at the same time the above-mentioned three
failure flags F_FSKDN, F_FSKDRDNB, and F_FSKDRDNC are all set to 0.
Then, the steps 156 and 157 are executed as described above,
followed by terminating the present process.
On the other hand, if the answer to the question of the step 161 is
negative (NO), i.e. if RATIO.gtoreq.RTDRJD holds, which means that
both of the engine torque TQEG and the throttle valve opening TH
are considerably large, and at the same time the belt 24 is
slightly slipping, the process proceeds to a step 164 in FIG. 16,
wherein it is determined whether or not the timer value TMDRDNJD of
the first OD-side determination timer referred to hereinabove is
equal to or larger than a predetermined second DR-side reference
value TMDRJ2 (corresponding to e.g. 5 seconds).
If the answer to this question is affirmative (YES), i.e. if both
of the engine torque TQEG and the throttle valve opening TH are
considerably large, and a state where the belt 24 is slightly
slipping has continued for a time period correspond to the
predetermined second DR-side reference value TMDRJ2 or longer, it
is judged that the DR solenoid valve 26b is fixed in the open
state, and the step 163 is executed. Then, the steps 156 and 157
are executed as described above, followed by terminating the
present process.
Referring again to FIG. 15, if either of the answers to the
questions of the steps 159 and 160 is negative (No), i.e. if the
engine torque TQEG is relatively small, or if the throttle valve
opening TH is not very large, the process proceeds to a step 165 in
FIG. 16, wherein it is determined whether or not the timer value
TMDRDNJ2 of the second OD-side determination timer is equal to or
larger than a predetermined OD-time DRDN-side reference value
TDRDNJD2 (corresponding to e.g. 15 seconds).
If the answer to this question is negative (NO), the steps 169 and
157 are executed, followed by terminating the present process. On
the other hand, if the answer to the above question is affirmative
(YES), i.e. if a state in which no significant slippage of the belt
24 is occurring, and the engine torque TQEG is relatively small or
the throttle valve opening TH is not very large has continued for a
predetermined time period corresponding to the predetermined
OD-time DRDN-side reference value TDRDNJD2 or longer, the process
proceeds to a step 166, wherein the timer value TMDRDNJD of the
first OD-side determination timer is set to 0.
Then, the process proceeds to a step 167, wherein so as to indicate
that there has occurred at least one of the fixation of the DR
solenoid valve 26b in the fully-open state and the fixation of the
DN solenoid valve 27b in the fully-closed state, the OD-time DRDN
failure flag F_FSKDRDNC is set to 1, and at the same time the above
three failure flags F_FSKDR, F_FSKDN, and F_FSKDRDNB are all set to
0. Then, the steps 156 and 157 are executed as described above,
followed by terminating the present process.
Next, the LOW-side determining process at the step 125 will be
described with reference to FIG. 18. This process is for
determining whether or not the DR solenoid valve 26b and the DN
solenoid valve 27b are both normal, or whether or not there has
occurred at least one of the fixation of the DR solenoid valve 26b
in the fully-closed state and the fixation of the DN solenoid valve
27b in the fully-open state. More specifically, the LOW-side
determining process is carried out as follows:
First, in a step 180, both of the respective timer values TMDRDNJD
and TMDRDNJ2 of the first OD-side determination timer and second
OD-side determination timer are set to 0. Then, the process
proceeds to a step 181, wherein it is determined whether or not the
stop-time LOW-side flag F_INGLOWJD set by the stop-time
transmission ratio determining process is equal to 1.
If the answer to this question is negative (NO), i.e. if the
transmission ratio RATIO is not in the stop-time LOW-side range
(RTINGLO.ltoreq.RATIO.ltoreq.RTINGLOH), the process proceeds to a
step 194, wherein the timer value TMDRDNBJD of the LOW-side
determination timer is set to 0.
Next, the process proceeds to a step 195, wherein the above four
failure flags F_FSKDR, F_FSKDN, F_FSKDRDNB, and F_FSKDRDNC are all
set to 0. Then, the process proceeds to a step 196, wherein the
timer value CTOKDRNS of the DRDN normality provisional
determination counter is set to 0, followed by terminating the
present process.
On the other hand, if the answer to the question of the step 181 is
affirmative (YES), i.e. if the transmission ratio RATIO is in the
stop-time LOW-side range, which means that
RTINGLOL.ltoreq.RATIO.ltoreq.RTINGLOH holds, the process proceeds
to a step 182, wherein it is determined whether or not the throttle
valve opening TH is equal to or larger than a predetermined
LOW-side reference value THDRDNBJD (e.g. 5%).
If the answer to this question is negative (NO), i.e. if the
accelerator pedal is not stepped on by the driver, causing the
throttle valve to be almost fully closed, the steps 194 to 196 are
executed as described above, followed by terminating the present
process. On the other hand, if the answer to the question of the
step 182 is affirmative (YES), which means that the accelerator
pedal is stepped on by the driver, causing the throttle valve to be
open, the process proceeds to a step 183, wherein it is determined
whether or not the vehicle speed VP is equal to or higher than a
predetermined LOW-side reference value VDRDNBJD (predetermined
vehicle speed: e.g. 15 km/h).
If the answer to this question is negative (NO), i.e. if the
vehicle speed VP is low, the steps 194 to 196 are executed as
described above, followed by terminating the present process. On
the other hand, if the answer to the above question is affirmative
(YES), i.e. if the vehicle speed VP is not low, the process
proceeds to a step 184, wherein it is determined whether or not the
target transmission ratio RATTGT is lower than a predetermined
LOW-side reference value RTTGDRDNB (e.g. 1.5).
If the answer to this question is negative (NO), i.e. if the target
transmission ratio RATTGT has not been changed from the LOW side to
the OD side, the steps 194 to 196 are carried out as described
above, followed by terminating the present process. On the other
hand, if the answer to the above question is affirmative (YES),
i.e. if the target transmission ratio RATTGT has been changed from
the LOW side to the OD side, the process proceeds to a step 185,
wherein it is determined whether or not the transmission ratio
RATIO is within a predetermined fixation determining LOW-side range
(low-speed range). The fixation determining LOW-side range
(RTDRDNBL.ltoreq.RATIO.ltoreq.RTDRDNBH) is set to the same range as
the stop-time LOW-side range, as described hereinbefore. More
specifically, the upper and lower limit values RTDRDNBH and
RTDRDNBL are set to the same values as the LOW-side upper and lower
limit values RTINGLOH and RTINGLOL, respectively. It should be
noted that the fixation determining LOW-side range may be set to a
range wider or narrower than the stop-time LOW-side range.
If the answer to the question of the step 185 is negative (NO),
i.e. if the transmission ratio RATIO is not in the fixation
determining LOW-side range, it is judged that the DR solenoid valve
26b and the DN solenoid valve 27b are both normal, so that the
process proceeds to a step 186, wherein the timer value TMDRDNBJD
of the LOW-side determination timer is set to 0, and then to a step
187, wherein the timer value CTOKDRNS of the DRDN normality
provisional determination counter is incremented by 1.
Then, the process proceeds to a step 188, wherein the above four
failure flags F_FSKDR, F_FSKDN, F_FSKDRDNB, and F_FSKDRDNC are all
set to 0. Thereafter, the process proceeds to a step 189, wherein
it is determined whether or not the timer value CTOKDRNS of the
DRDN normality provisional determination counter is equal to or
larger than a predetermined DRDN normality reference value COKDRDNS
(e.g. 1500).
If the answer to this question is negative (NO), the present
process is immediately terminated. On the other hand, if the answer
to the question is affirmative (YES), i.e. if a state in which both
of the DR solenoid valve 26b and the DN solenoid valve 27b can be
regarded as normal has been detected a predetermined number (equal
to the value of COKDRDNS) of times or more, the process proceeds to
a step 190, wherein the aforementioned four normality flags F_OKDN,
F_OKDR, F_OKDRDNB, and F_OKDRDNC are all set to 1 to indicate that
both of the DR solenoid valve 26b and the DN solenoid valve 27b are
normal, followed by terminating the present process.
On the other hand, if the answer to the question of the step 185 is
affirmative (YES), i.e. if the transmission ratio RATIO is in the
fixation determining LOW-side range
(RTDRDNBL.ltoreq.RATIO.ltoreq.RTDRDNBH), it is judged that there
has occurred at least one of the fixation of the DR solenoid valve
26b in the fully-closed state and the fixation of the DN solenoid
valve 27b in the fully-open state, so that the process proceeds to
a step 191, wherein it is determined whether or not the timer value
TMDRDNBJD of the LOW-side determination timer is equal to or larger
than a predetermined failure reference value TDRDNBJD
(corresponding to e.g. 10 seconds).
If the answer to this question is negative (NO), the present
process proceeds to a step 193, wherein the aforementioned four
normality flags F_OKDN, F_OKDR, F_OKDRDNB, and F_OKDRDNC are all
set to 0. Then, the step 196 is executed, followed by terminating
the present process.
On the other hand, if the answer to the question of the step 191 is
affirmative (YES), i.e. if a state, in which at least one of the
fixation of the DR solenoid valve 26b in the fully-closed state and
the fixation of the DN solenoid valve 27b in the fully-open state
can be regarded as occurring, has continued for a predetermined
time period (corresponding to the predetermined failure reference
value TDRDNBJD) or longer, the process proceeds to a step 192,
wherein to indicate that there has occurred at least one of the
fixation of the DR solenoid valve 26b in the fully-closed state and
the fixation of the DN solenoid valve 27b in the fully-open state,
the LOW-time DRDN failure flag F_FSKDRDNB is set to 1, and at the
same time the above-mentioned three failure flags F_FSKDR, F_FSKDN,
and F_FSKDRDNC are all set to 0. Then, the steps 193 and 196 are
executed as described above, followed by terminating the present
process.
As described in detail heretofore, in the FIG. 13 fixation
determining process for determining whether fixation of any of the
DR solenoid valve 26b and the DN solenoid valve 27b has occurred,
the determination is carried out based on the transmission ratio
RATIO, the throttle valve opening TH, the engine torque TQEG, the
vehicle speed VP, and so forth. This is based on the following
logic:
In the continuously variable transmission 20 according to the
present embodiment, when the vehicle 3 is standing, the
transmission ratio RATIO is controlled to be in the fixation
determining LOW-side range (RTDRDNBL.ltoreq.RATIO.ltoreq.RTDRDNBH).
Therefore, in the FIG. 14 stop-time transmission ratio determining
process, if the transmission ratio RATIO is in the stop-time
LOW-side range (RTINGLOL.ltoreq.RATIO.ltoreq.RTINGLOH), it is
presumed that the DR solenoid valve 26b and the DN solenoid valve
27b are both normal. Further, if both of the DR solenoid valve 26b
and the DN solenoid valve 27b are actually normal, when the target
transmission ratio RATTGT is changed, after the standing start of
the vehicle 3, to the OD side as indicated by a broken line in FIG.
19, the actual transmission ratio RATIO as well should be changed
such that it follows the change in the target transmission
ratio.
In contrast, if the answers to the questions of the steps 181 to
185 are all affirmative (YES), which means that the throttle valve
is open (TH.gtoreq.THDRDNBJD), the vehicle has been started
(VP.gtoreq.VDRDNBJD), and at the same time, in spite of the target
transmission ratio RATTGT having been changed from the LOW side to
the OD side (RATTGT<RTTGDRDNB), the transmission ratio RATIO is
in the fixation determining LOW-side range as indicated by a solid
line in FIG. 19, it is possible to presume occurrence of the
following state: irrespective of shortage of oil pressure from the
hydraulic circuit 28, the drive pulley 22 is held at the LOW-side
wide width of the belt groove owing to the fixation of the DR
solenoid valve 26b in the fully-closed state, which inhibits the
supply of oil pressure to the DR oil chamber 26a, or alternatively
the driven pulley 23 is held at the LOW-side narrow width of the
belt groove, owing to the fixation of the DN solenoid valve 27b in
the fully-open state, which causes continued supply of oil pressure
to the DN oil chamber 27a.
Therefore, when such a state has continued for the predetermined
time period corresponding to the predetermined failure reference
value TDRDNBJD (between t1 to t2) or longer, it can be determined
that the transmission ratio RATIO is not changed but held in the
above LOW-side range due to the fixation of the DR solenoid valve
26b in the fully-closed state and/or the fixation of the DN
solenoid valve 27b in the fully-open state
(F_FSKDRDNJB.rarw.1).
Further, in the FIG. 14 stop-time transmission ratio determining
process, when the transmission ratio RATIO during stoppage of the
vehicle 3 is within the stop-time OD-side range
(RTINGODL.ltoreq.RATIO.ltoreq.RTINGODH), it can be presumed that
there has occurred the following state: Irrespective of shortage of
oil pressure from the hydraulic circuit 28, the drive pulley 22 is
held at the OD-side narrow width of the belt groove owing to the
fixation of the DR solenoid valve 26b in the fully-open state,
which causes continued supply of oil pressure to the DR oil chamber
26a, or alternatively the driven pulley 23 is held at the OD-side
wide width of the belt groove owing to the fixation of the DN
solenoid valve 27b in the fully-closed state, which inhibits the
supply of oil pressure to the DN oil chamber 27a.
Further, in the case where the transmission ratio RATIO during
stoppage of the vehicle 3 is within the stop-time OD-side range, as
shown in FIG. 20, after-the start of the vehicle 3, when the engine
torque TQEG is not very large (TQEG<TQDRJD), or when the
throttle valve opening TH is not very large (TH<THDRJD), the
urging force of the return spring prevents occurrence of a
significant slippage between the drive pulley 22 and the belt 24 or
between the driven pulley 23 and the belt 24, thereby enabling the
vehicle 3 to travel. Therefore, although it is impossible to
determine whether the DR solenoid valve 26b is fixed in the
fully-open state or whether the DN solenoid valve 27b is fixed in
the fully-closed state, it is possible to presume that at least one
of the solenoid valves is fixed irrespective of shortage of oil
pressure from the hydraulic circuit 28.
Therefore, when such a state has continued for the predetermined
time period corresponding to the predetermined reference value
TDRDNJD2 (between t11 to t12) or longer, it is possible to
determine that there has occurred at least one of the fixation of
the DR solenoid valve 26b in the fully-open state and the fixation
of the DN solenoid valve 27b in the fully-closed state
(F_FSKDRDNC.rarw.1) irrespective of shortage of oil pressure from
the hydraulic circuit 28.
Further, in the case where the transmission ratio RATIO during
stoppage of the vehicle 3 is within the stop-time OD-side range, as
shown in FIG. 21, after the start of the vehicle 3, when the
transmission ratio RATIO is not changed from the OD side to the LOW
side (RATIO<RTDNJD) in spite of the engine torque TQEG being
considerably large (TQEG.gtoreq.TQDRJD), it can be presumed that no
slippage is occurring between the drive pulley 22 and the belt 24
or between the driven pulley 23 and the belt 24 although torque
input to the drive pulley 22 is large. Such a state does not occur
even when the driven pulley 23 is actuated to the OD-side wide
width due to the fixation of the DN solenoid valve 27b in the
fully-closed state, or even when oil pressure from the hydraulic
circuit 28 is not sufficient, so long as the DR solenoid valve 26b
is normal, since the transmission ratio RATIO is changed to a value
on the LOW side, but occurs only when the DR solenoid valve 26b is
fixed in the fully-open state.
Therefore, when such a state has continued for the predetermined
time period corresponding to the predetermined DR-side reference
value TDRJD (between t21 to t22) or longer, it is possible to
determine that the DR solenoid valve 26b is fixed in the fully-open
state (F_FSKDR.rarw.1) irrespective of shortage of oil pressure
from the hydraulic circuit 28. In short, the failure of the DR
solenoid valve 26b can be identified.
Further, in the case where the transmission ratio RATIO during
stoppage of the vehicle 3 is within the stop-time OD-side range, as
shown in FIG. 22, in spite of the throttle valve being open
(TH.gtoreq.THDRDNJD), if the vehicle speed VP remains low
(VP<VDRDNJD), and at the same time the transmission ratio RATIO
is changed from the OD side to a considerably high value on the LOW
side (RATIO.gtoreq.RTDNJD), it can be presumed that oil pressure is
not supplied to the DN oil chamber 27a due to the fixation of the
DN solenoid valve 27b in the fully-closed state irrespective of
shortage of oil pressure from the hydraulic circuit 28, causing a
significant slippage of the belt 24 between the driven pulley 23
and the belt 24.
Therefore, when such a state has continued for the predetermined
time period corresponding to the predetermined DN-side reference
value TDNJD (between t31 to t32) or longer, it is possible to
determine that the DN solenoid valve 27b is fixed in the
fully-closed state (F_FSKDN.rarw.1) irrespective of shortage of oil
pressure from the hydraulic circuit 28. In short, the failure of
the DN solenoid valve 27b can be identified.
As described hereinbefore, according to the failure determination
system 1 of the present embodiment, it is possible to determine
whether or not there has occurred at least one of the fixation of
the DR solenoid valve 26b in the fully-open/fully-closed state, and
the fixation of the DN solenoid valve 27b in the
fully-open/fully-closed state, irrespective of shortage of oil
pressure from the hydraulic circuit 28. Additionally, when the
conditions shown in FIG. 21 or FIG. 22 are satisfied, the failure
of the DR solenoid valve 26b or the DN solenoid valve 27b can be
identified, which makes it possible to easily repair the
continuously variable transmission 20 simply by replacing the DR
solenoid valve 26b or the DN solenoid valve 27b, and thereby
enhance maintainability of the continuously variable transmission
20.
It should be noted that the present embodiment is a case in which
the crank angel sensor 40 is employed as the rotational speed
parameter-detecting means, this is no limitative, but the
rotational parameter-detecting means may be implemented by any
suitable device that can detect the rotational speed parameter
indicative of the rotational speed of the power source, such as the
engine 4. For example, in place of the crank angel sensor 30, the
drive-pulley rotational speed sensor 44 or the driven-pulley
rotational speed sensor 45 may be employed as the rotational speed
parameter-detecting means. In this case, although in the present
embodiment, to discriminate between the travel incapability state
owing to the failure of the SC solenoid valve 33b and the
hill-climbing of the vehicle 3, in the step 20, the first travel
incapability reference value NERUNNG is calculated, and in the step
28, it is determined whether or not the engine speed NE is equal to
or higher than the first travel incapability reference value
NERUNNG, in place of these operations, it is only required to
perform the following operations:
In the step 20, a travel incapability reference value NDRRUNNG is
calculated according to the throttle valve opening TH, and in the
step 28, it is determined whether or not the drive-pulley
rotational speed NDR is equal to or higher than the travel
incapability reference value NDRRUNNG. If the answer to this
question is affirmative (YES), similarly to the embodiment
described above, it is only required to execute the step 29 et seq.
Further, in place of the drive-pulley rotational speed NDR, the
transmission ratio RATIO or the driven-pulley rotational speed NDN
may be employed. More speficailly, in the step 20, a travel
incapability reference value RATRUNNG (or NDNRUNNG) is calculated
according to the throttle valve opening TH, and in the step 28, it
is determined whether or not the transmission ration RATIO (or the
driven-pulley rotational speed NDN) is equal to or higher than the
travel incapability reference value RATRUNNG (or NDNRUNNG). If the
answer to this question is affirmative (YES), similarly to the
embodiment described above, it is only required to execute the step
29 et seq. As described above, the travel incapability referncde
values NDRRUNNG, RATRUNNG, and NDNRUNNG are each set as a value
equivalent to the first travel incapability reference value
NERUNNG.
It should be noted that the drive source is not limited to the
engine 4 employed in the embodiment, but any electric motor or
other suitable means may be employed as the drive source so long as
it generates power. Further, in the case of an electric motor being
employed as the drive source, the rotational speed of the
rotational shaft of the electric motor may be directly detected by
a sensor, or may be estimated by detecting a current value
indicative of the rotational speed of the electric motor. Further,
as the failure determination process for the SC solenoid valve 33b,
a process for determining an electric fault (a disconnection or a
short circuit) of the solenoid of the SC solenoid valve 33b may be
carried out separately from the failure determination process
executed in the above-described embodiment. With this
configuration, it is possible to discriminate the fixation of the
valve element of the SC solenoid valve 33b from the electric fault,
thereby making it possible to locate a faulty part of the SC
solenoid valve 33b. Further, as the failure determining process for
determining the failure of any of the two solenoid valves 26b and
27b, a process for determining an electric fault (a disconnection
or a short circuit) of the solenoids of the two solenoid valves 26b
and 27b may be carried out separately from the FIG. 13 fixation
determining process executed in the embodiment. With this
configuration, it is possible to discriminate the fixation of the
valve element of the solenoid valve 26b or 27b from the electric
fault, thereby making it possible to locate a faulty part of the
solenoid valve 26b or 27b.
The control valve for the start clutch is not limited to the SC
solenoid valve 33b employed in the embodiment, but any suitable
control valve may be employed so long as it is capable of
controlling the oil pressure to be supplied to the start clutch 30.
Further, the drive-side control valve and the driven-side control
valve are not limited to the DR solenoid valve 26b and the DN
solenoid valve 27b employed in the embodiment, but any valves may
be used as the control valves so long as they are capable of
controlling oil pressures supplied to the DR oil chamber 26a for
the drive pulley 22 and the DN oil chamber 27a for the driven
pulley 23. For example, as the control valve for the start clutch,
the drive-side control valve and the driven-side control valve,
electric motor valves may be used or mechanical valves (e.g. spool
valves) whose valve openings are controlled by control pressures
supplied thereto may be used.
Further, although in the embodiment, the transmission ratio RATIO,
which is a ratio between the rotational speeds of the drive pulley
22 and the driven pulley 23, is calculated in the state where the
rotation of the engine 4 is transmitted during stoppage of the
vehicle 3 up to the continuously variable transmission 20 via the
forward/backward travel-switching mechanism 10 and at the same time
the continuously variable transmission 20 is disconnected from the
drive wheels 7 by the start clutch 30, and the failure of the
solenoid valves 26b and 27b is determined based on the transmission
ratio RATIO calculated during stoppage of the vehicle 3, this not
limitative, but the failure determination system 1 according to the
present invention can be applied to a vehicle without the start
clutch 30 between the continuously variable transmission 20 and the
start clutch 30, which during stoppage of the vehicle, torque
transfer from the engine 4 to the continuously variable
transmission 20 is inhibited by slippage of a clutch or a torque
converter arrange between the continuously variable transmission 20
and the engine 4. In such a case, it is only required that a value
of the transmission ratio RATIO calculated immediately before
stoppage of the vehicle is used in place of a value of the same
calculated during stoppage thereof, to thereby execute
determination of failure of the solenoid valves 26 and 27b
similarly to the embodiment.
Further, the vehicle start operation-detecting means is not limited
to the throttle valve opening sensor 41 employed in the embodiment,
but the accelerator opening sensor or any other suitable means may
be used so long as it is capable of detecting the start operation
of the vehicle 3.
Also, the transmission is not limited to the continuously variable
transmission 20 employed in the embodiment, but any suitable
transmission that performs speed varying operation may be employed.
For example, it is possible to employ an automatic transmission of
a torque converter type, or a so-called automatic MT in which an
electromagnetic force instead of a manual operating force performs
the speed varying operation.
It is further understood by those skilled in the art that the
foregoing is a preferred embodiment of the present invention, and
that various changes and modifications can be made without
departing from the spirit and scope thereof.
* * * * *